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and Other Physiological Media. Vincent E. Bower, Maya Paabo, and Roger G. Bates ..... [9] R. A. Robinson and R. H. Stokes, Electrolyte solutions, second ed. (Academic ..... for solid-disk dielectric specimens, A. E . Scott and William. P . Harris.
JOURNAL OF RESEARCH of the National Bureau of Standards-A. Physics and Chemistry Vol. 65A, No. 3, May- June 1961

A Standard for the Measurement of the pH of Blood and Other Physiological Media Vincent E. Bower, Maya Paabo, and Roger G. Bates (F ebruar y 14, 196 1)

J -

j

' A b uff er sol ution containing p otassiu m dihydrogen p hosphate (0.008695 m olal) an d d isodiu m h ydrogen phosphate (0.03043 molal) is p roposed as a pH stand ard for t he p hysiologically important r a nge, pH 7 to 8. The proposed stand ard solut ion is prepared by dissol ving 1.179 g (air weight ) of po tassium dihyd rogen phosp hate and '1.3 03 g (a ir weight) of disodium h ydrogen phosphate i n a mmonia-free water a nd di lut in g to 1 liter at 25 °C . The ioni c strength is 0.1. Standa rd pH val ues (pH .) were assign ed t o t his r eference solution at tem peratur es from 0 to 50 °C by mea ns of emf m eas uremen ts of h ydrogen-sil ve r chlorid e cells wit hou t liquid jun ction. Th e acti vity coeffi cient of chl ori de ion, upon whi ch t he assignment of pH. d epends, was eval uate d by means of a r ece nt ly proposed convention. By t his m eans, '-standard values precise to ± 0.001 u ni t co uld be deri ved from t he emf data. At 25 ° C pH . is 7.4 14 , a nd at 38 ° C it is 7.382. The operatio na l consiste ncy of t hese stand ard values wit h t hose for t he 0.025-m equ imo lal p hosp hate bu ff er (one of t he KBS p ri mar y s ta ndards) was d em o nst rated .

I . Introduction The acid-ba se beh avior of blood and o ther physiological fluids h as b een ~widely s Ludied in recen t year s in m edical and biological la boratories in an a t temp t to discover t be relationships that exist among physiological fun ctions, pathological condi tions, and pH. Many of these fluids are well buffered, and t he detection of any sys tem atic variation of pH with physiological condi tion would therefore b e exp ected to r equire precise measuring equipmen t. Such equipmen t is readily available commer cially in t he form of the n ewer highly-sensitive pH mcter s with a gl ass electrode. Experience has shown that, wi th the exer cise of care, the inves tiga tor or clinician can ob tain glasselectrode pH valu es, for reduced blood and other body fluids, th at agr ee wi thin ± 0.01 uni t wi th pH numbers obtained by m eans of the hydrogen electrode [1]. J Th e high degr ee of sta bili ty in these biological systems and in the m easuring appara tus sugges ts that blood pH m easurem en ts with a precision of 0.00 5 unit (or even 0.001 unit) could profitably b e m ade. M eaningful comparisons of highly precise resul ts of different laboratories could th en b e m ade, provided that a sui table referen ce standard wer e available. Unfortunately, useful comparisons of pH data , quo ted to 0.001 uni t, from differen t sources h ave in general b een impossible. The difficulty can be a t tributed to the fact t ha t in all of the m a.jor conventions definin g pH [2], a 110n thermod yn amic conven tion concerning single-ion s,ctivi ty coeffi cien ts is by n ecessity adop ted . A t th e present time no single convention fo1' definin g a n ionic activity is widely accepted . Al th ough the conven tions used her etofore to estimat e single-ion activity coeffi cien ts are " reasonable" and yield pH numbers consisten t 1

:Figures in brackets indicate the literature references at the end of this paper

wi th each other to within 0.01 uni t, they alllaek tb e exactn ess required for assignmen t of values to 0.001 uni t. Bates and Guggenheim [3], in a r ecen t repor t to the International Union of Pure and Applied Chemistry, have proposed a very simple and precise way of defining the sin gle-ion activi ty for t he es tablishm en t of pH standards. By m eans of the convention they have et forth, pH valu es precise to wi thin 0.001 uni t m ay be assigned to selected standards in a r estricted sector of the pH r ange. E rrors due to th e faul ty response of th e gla ss electrode are minimized if t he pH of the standard is close to that of th e unknown. The availability of a precise pH tandard in the physiologicall'ange would ass ist m ateri ally in th e exact comparison of pH measurem ents made on biological sys tems in differen t lab ora tori es. It is the purpose of this p aper to propose, as a physiological pH standard, a phosphate buffer mixture with a pH of abou t 7.4 and to assign pH values to this standard. The proposed stand ard h as t h e following composition : KH 2P0 4(0.008695 molal), N a2HP04(0.03043 molal).

2. Method of Defining pHs In order to avoid the th eoretical and practical difficulties inher en t in t he estimation of liquid jun ction poten tials, standard pH values h ave b een b ased upon measuremen ts of cells wi thou t liquid junction. In this work , hydrogen and silver-sil ver chloride electrodes wer e used , measuremen ts b ein g made of the electromo tive force of the cell : P t;H z(g,l atm ), KH zP0 4 (0.008695 molal), Na2HP04(0.03043 molal), Cl- ,AgCl ;Ag.

The electromotive for ce, E, of cell (A ) is r elated to t he standard electrode po ten tial (EO) of th e silver -

267 585402- 61- -9

(A)

silver-chloride electrode [4] and to the activities of the hydrogen and chloride ions in the solution by the reJation (1)

where a is the activity (molal basis) of the ionic species designated by the subscript. R earrangement, conversion to decadic logarithms, and substitution of mC(YCI for aCI yields a thermodynamic acidity function, - loge'YH'Y ClmH): - log ('YH 'YClmH) = (E -EO)F/(2.3026RT) + 10g mCI. (2)

In eq (2) , m is the molality and 'Y is the activity coefficient, on the molal scale, of the ions designated by the subscripts. For satistactory reproducibility and constancy of the electromotive force , a finite amount of chloride must be present in the buffer solution. Nevertheless, it is the acidity function of the chloride-free buffer solution that is desired . The value of - loge'YH'Y ClmH) was therefore measured at each of three low chloride concentrations, namely 0.005 m, 0.010 m, and 0.015 m and - log('YH'Yc lmH)O , the limit of - log ('YH'YClmH) as m Cl approaches zero, was obtained by extrapolation. If the standard pH (denoted pH,) is defined formally as - log aH or - log mH'YH, then pH,= - log ('YH'YClmH)o+ log'Ygl.

(3)

It will be observed that, according to eq (2), - log('YH'Yc,mH) is a measurable quantity. On the contrary, 'Y 2;1 in eq (3) is the activity coefficient of a single ion, a quantity that is not measurable. To obtain pH" therefore, some assumption must be made, or convention adopted, to evaluate 'Y l'n . For the purposes of assigning standard pH values to the standard buffers already proposed by the National Bureau of Standards, various assumptions have been used to estimate 'Y l'a [5,6,7] . If the ionic strength does not exceed 0.1 , the numerical values of 'Y8 (obtained from the above assumptions) can all be closely represented by the following form of the Debye-Huckel equation:

° - I og'YCI=

A-/P.

1

+ BarVIl-r '

(4)

where Mis the ionic strength, ai is an adjustable "ionsize parameter", and A and B are constants dependent upon temperature and solvent. 2 In the last analysis, therefore, the differences among the conventions themselves can be expressed as differences in ai. Fortunately, all "reasonable" conventions for the definition of 'Y~I lead to substantially equivalent values for the pH, of the standard phosphate buffer (M= O.l) [10] . All of these values fall within ± 0.01 unit of the assigned NBS standard values for this buffer solution. The agreement at lower ionic strengths is even more satisfactory. , Tabulations of A and B are to be fouud in references [8] and [9].

Since there is r eally no apparent basis for choice among these assumptions, anyone of them may b e selected to represent 'Y~I . Bates and Guggenheim have proposed, in their report to the Analytical Chemistry and Physical Chemistry Sections of the International Union of Pure and Applied Chemistry, a value of Bai= 1.5 mole - ~~ kg~2 [3]. The pH values given in the present work are based upon eqs (3) and (4) and t his convention of Bates and Guggenheim.

3 . Experimental Procedures and Results

The cells used for the m easurements have been described in detail in a previous article [6]. Briefly , each cell consists of two electrode compartments and a chamber in which incoming hydrogen is saturated with the vapor over the buffer solution. The chamber terminates in a tube which leads to the jet in the hydrogen electrode compartment of the cell. Hydrogen gas escapes from the top of the hydrogen electrode compartment. The silver-silver chloride electrode compartment is connected to the hydrogen electrode compartment by a broad tube filled with the cell solution. The standard buffer solution selected was 0.008695 molal in potassium dihydrogen phosphate (molecular weight, 136.092) and 0.03043 molal in disodium hydrogen phosphate (molecular weight, 14l.982).3 These proportions wer e chosen with the intention of producing a solution of pH about 7.4 at 25°C and with an ionic strength of 0.1. The solvent used in this study was ammonia-free distilled water of conductivity no greater than 0.8 X IO- 6 ohm- 1 em-I. The phosphate salts were specimens of NBS Standard Sample 186Ib (KH2P0 4 ) and 186IIb (N a2HP04), dried for an hour in a oven at 110 °C and used without further treatment. The ' potassium chloride was taken from a highly purified sample whose manner of preparation and purification . has been described elsewhere [11]. Twenty cells containing the phosphate buffer with low concentrations of chloride (0.005 m, 0.010 m, or 0.015 m) were made up. The emf of 13 of these cells was measured over the temperature range 0 to 50°C; five cells were studied over the range, 25 to 50°, one cell over the range 0 to 40°, and one cell at only three temperatures. After the emf had been corrected to the standard partial pressure of hydrogen (760 mm), the acidity function - loge 'YH'YClmH) for each cell was calculated by means of eq (2) . Values of - log ('YH'YC1mH) arc listed in table l. For these calculations, R was taken as 8.3147 j mole- I deg- 1 and F' as 96 ,495.4 coul equiv- 1 [12] .

I

4 . Assignment of p Hs Values The - log(YH'Yc lmH) was found to b e a linear function of mCb and the limiting value, - log ('Y H'Y c lmH)O (at mCI = O), was evaluated by the method of least 3 The density at 25 ° 0 of this solution is 1.0020 glm!. A solutiou of this com· position may be made by dissolving 1.179 g (air weight) KH, PO, and 4.303 g (air weight) Na,HPO, ill water and diluting to 1 liter at 25 °0 .

268

T AB I_E

Electromotiv e f Ol'ce of cell (A ) containing the phosphate buffer solution : 0.008695 wi th three molali ties of added J( Cl

1.

Tn

IU!2PO. , 0.0304 3

III

Na 2TIPO.

Temprrature °C

KCI, molality

0

5

0.77510 . 77481 .77502 . 774~4 . 77537 .77531

0.78078 . 78037 . 7 ~0 1 5 . 780 12 . 78080 . 78053

10

15

20

25

0.79187

0. 79754

0. 80324 . 80308 .80322 . 80295 . 80336 .80326 . 80330 .80322

30

35

38

40

.81796 . 81791 .81810 . 81794 .81798 .81798

0.82018 -----_.--- -.82018 . 82021 . 82048 . 82025 . 82025 .82036

45

50

---0. 005 . 005 . 005 .005 . 005 . 005 . 005 .005 . 010 . 010 .010 . 010 . 010 .010 .010 . 010 . 015 . 015 . 015 . 015

0.7863 l ------------

.7 507 .78512 .78550 . 78612

------------ ----_. --._- . 79168 .79177 . ?D198 . 79149

. 79745 . 79756 . 79771 . 79i22

--- - -------- ------.-. _. - ---- ----- --- -----------. --------.-------------- ------------ - - - - --- ----- --------._-- --._- - ------

. 758,07 . 7583.5 .75862 . 75859 . 75869 .75868

. 76392 .76380 .76374 .76384 . 76379 . 76381

. 76912 . 76899 .76903 . 7691.5 .76920 .76922

.77442 . 77424

.77-m

. 7744.1 .77438 .77435

. 78512

. 77970 . 779.5!,; . 77946 . 77989 . 77979 . 77970

.74873 . 7'1%9 . 74895 ------------

-

. 75900 . 75392 . 7.1360 .75875 .75373 .75895 ------- ---- -- - ---- -----

. 76406 .76383 .76394

. 76923 .711891; . 76918

------------

--- -- -- - - - -

0.81457

0.81800

--- -- ----- -.

-- ---- ---.--

. 80888 .80893 .80902 .80884 . 80884 . 80886

.81451 .81434 .81469 . SHOO . 81435 . 81450

O. R2577

0.83149

-- -- -------- ----.--- ---

. 8258G

.82606

.83145 . 83180

- --- ------.- - -. ---- . ---

. 82578 . 8256B .82612

. 83142 .83122 .83151

. 78506 . 78500 . 78517 . 78497 . 78527

. 79047 . 79070 . 79044 . 79056 .79048 . 79054 . 79026 • 7904S

.79584 . 79588 . 79568 . 79588 .79587 .79596 . 79563 .79585

. 79916 . 79909 .79903 . 79911 .79906 . 79921 . 79887 .79920

.80124 . 80115 .80136 .80133 .80 l 29 .80143 . 80107 .80135

.80672 .8061\3 . 80667 .80678 . 80662 . 80541 • R0659 .80673

. 81222 .81200 . 81188 .81224 .81222 .8123;' . 8ll95 .81195

. 77427 .77421 .77449 . 77446

. 77966 . 77949 . 77947 . 77978

. 78478 .78443 . 78476 . 78498

.78800 . 78768 . 78779 . 78803

. 78993 .78966 . 78999 .79017

. 79513 .79501 .79521 . 79546

.80036 . 80042 .80067 .80049

. 78b08 . 78006

--.-._---- -- ------------ -------- - --- -------_ .. _-- ----------------------- ------------ -- - - - -----.- ---- - - - - - --- --------- - --

0. 80897 - -.- ----.---

squares. Figure 1 shows t he array of - log( an'Ycl) or - log (YnYc lmn) vttlues at two temper atures . Values of - log (YnYc ImH) 0 and the standard deviat ion (J' i) of the intercept are given in tftble 2. The quantities - logy Oc l computed from eq (4 ) arc also listed . The standard pHsval ues wer e d erived fro m - log (YHY C ImH ) 0 by eq (3). They are listed in the last colu mn of table 2 and ar c rep resented grap hically as a function of temper ature in figur e 2. The standard solution proposed here has an ioni c strength of 0.1 and a buffer ratio of 3.5 . The difference in pH r esult ing from sm all variations in t he concentration of one or both phosphates is given with sufficient accuracy by the followin g expression , based on the m ass law:

solution proposed h ere. Also assumed in th e derivation of eq 5 was the approximation YHPoi -= (ygl_)4= ('YH 2POi )4. It should be noted that n either of these phosphate salts is a strong enough acid or base to react appreciably with water. Hydrolysis correctio ns are therefore unnecessary, and the ratio of the concentrations of th e phosphate ions is th e same as the stoichiometric ratio of t he molalities of the two sal ts. The first term within the brace in eq (5) is given in table 2. The second quantity inside the braces may b e calculated from eq (4) with Bai= 1.5 mole -~kg ~ . For buffer solu bons composed of potassium hydrogen phosphate (ml) and disodium hydrogen phosphate (m2) , !L = ml + 3m2' 7.54

+ 3{log ygl(s) - log ygl(x) },

,-------,----~-----,----.------,

(5)

where x des ignates the solu tion of buffer ratio slightly different from 3.5, and/or ionic strength sli g htly different from 0.1, and where s designates th e standard

7. 52

7. 50 ,--- - - - - - - , - - - - - - - - , - - - - - - - - , - - - - - - - - ,

7.49~.~38.C o

7.48

g 0

7.48 -

o ,,'0 or.

7.47 L....._ _ _ _...L.._ _ _ _....!.._ _ _ _ _ _ _ _ _- - - '

go

7. 53

7. 44

,

7.52

7.40 7. 5 I -

7. 50 L....._ _ _ _...L.._ _ _ _....!.._ _ _ _---'_ _ _ _- - - '

0 .0 05

0 .010

0 . 015

0 . 020 7.36

M OLALITY OF KC I

- log ('Y JI'Yc lmn) of a solu tion 0.008695m in KH 2 PO. and 0 .03043 m i n Na2TIP0 4 as a function of molality of added chloride.

FI GU RE

L----..L'O- - - -2L O- - - -3..L0- - - -4L O----"50 TE M P~RAruRE

l.

269

2.

,·C

pI-I. of a soluti on 0.008695m i n K II, PO. and 0.03043 m i n Na2HPO. as a fun cti on of tempemture.

FIGU RE

TABLE

2.

pH.and - log(YHYClmH) 0 for the solution 0.008695 m in KH,PO, and 0.03043 m in N a,HPO,

tOC

- log('YH'YClmH) O

",

- log 'Y CI

pH . (experimental )

0 _______________ 5 _______________ 10 ______________ 15 ___ _______ ____ 20 ______________

7.6400 7.6052 7.5793 7. 5547 7.5374

0.0023 .0018 .0018 .00 17 .0019

0.1055 . 1062 .1070 . 1078 .1087

7.534 7.499 7.472 7.447 7.429

25 ______________

30 ______________ 35 __ ____ __ ______ 38 ________ ____ __ 40 ______ _____ ___

7.5234 7.5109 7.4985 7.4955 7.4934

.0011 .0011 . 0014 .0011 .0013

. 1095 . 1104 . 1114 . 1121 . 1125

7.414 7.400 7.387 7.383 7.381

45 _________ _____ 50 _______ __ _____

7.4863 7.4816

.0016 . 0018

. 1135 . 1146

7.373 7.307

T

2.3392 + 0.014798T.

3.

Recommended values of pH. at specified temperatures (values calculated from eq (6)) pH.

0 ________________ _ 5 ___________ _____ _ 10 _______________ _ 15 ___ ____________ _ 20 _______________ _ 25 ___________ ____ _

The" experimental" values of pHs listed in table 2 were smoothed with respect to the temperature (T) in OK by the method of least squares, with the following result : 1592.07

TABLE

(6)

Recommend ed values of pHs, calculated at specified temperatures from eq (6), are given in table 3.

7.531 7.501 7.47'1 7.450 7.430 7.413

pH. 30 ____________ _ 35 ____________ _ 38 ____________ _ 40 ____________ _ 45 ____________ _ 50 ___ ______ __ __

7.399 7. 387 7.382 7.379 7.373 7. 369

respectively, 0.550 and 0.546 pH unit. These values are in good agreement with the values of LlpHs given above, which were, of course, derived from the emfof cells without liquid junction. The internal consistency of the practical scale to a few thousandths of a unit in the physiological range therefore seems to have been demonstrated. By a similar series of measurements at 25 DC, it has already b een shown that the standard phthalate (pH 4.006), phosphate (PH 6.863), and borax (PH 9.183 ) buffer solutions are consistent among themselves to about ± 0.003 unit [14]. In the authors' opinion, these intercomparisons constitute an experimental justification for the assignment of a third decimal to the pHs for the primary standards of intermediate pH .

5. Internal Consistency of the Standard pH Scale It was considered desirable to test the operational consistency of the pHs values defined in this paper with those defin ed some years ago by Bates and Acree for the equimolal 0.025 m phosphate buffer (0.025 m KH 2P0 4, 0.025 m N a2HP04) [6]. To this end, emf measurements were made with a symmetric cell [13] consisting of two hydrogen electrode compartments connected by a bridge of saturated potassium chloride. The standard equimolal phosphate buffer solution was placed in one of the hydrogen electrode compartments and the solution of buffer ratio 3.5 in the other. The emf between the two hydrogen electrodes yields the operational pH difference (LlpH ) , which can then be compared with the difference of assigned pH , (LlpHs). The assignment of pHs is made by eq (3), where log I'~I is defined by the Bates-Guggenheim convention (and therefore constant for a given value of the ionic strength).4 The difference in pHs is therefore equal to the difference between the values of - log('YHl'c lmH)O for the two solutions, namely 7.523 - 6.972 or 0.551 at 25°C and 7.496 -6. 952 or 0.544 at 38 °C. M easurements of the symmetrical cell 'w ith liquid junction were made at 25 and 38 DC . The experimental values of LlpH at the two temperatures were, , The earlier aSSignment of p H . to the phosphate b uffer solution waS based on a more complex formula for estimating 'Y~l [6] . The two procedures lead to values of pH. for the equimolal phosphate st.andard that differ by only 0.003 unit at 25 °C .

6 . References [1] J . Sendroy, Jr. , page 55 in Symposium on pH m eas urement, ASTM Special Technical Publication No. 190, (American Society for T esting Materials, Philad elphia, Pa., 1957). [2] British Standard 1647 ; 1950 (British Standards Institution, London, 1950) . Japa nese Industri al Standard Z 8802-1958 (Japa nese Standards Association, Tokyo, 1958). R. G. Bates, J. Research NBS, 47, 433 (1951 ) RP2268. [3] R. G. Bates and E. A. Guggenheim, Pure and Applied Chemistry 1, 163 (1960). [4] R. G. Bates and V. E. Bower, J . R eaearch NBS 53, 283 (1954) RP2546. [5] W. J . Hamer, G. D . Pinching, an d S. F. Acree, J. R esearch NBS 36, 47 (1946) RP1690. [6] R. G. Bates and S. F. Acree, J . R esearch NBS 30, 129 (1943) RP1524; 34, 373 (1945) RP1648. [7] G. G. Manov, N. J. DeLollis, P. W. Lindvall, and S. F. Acree, J. Research NBS 36, 543 (1946) RPl72l. [8] G. G. Manov, R . G. Bates, W. J. H a mer . and S. F. Acree, J . Am. Chern. Soc. 65, 1765 (1943 ) . [9] R. A. Robinson and R. H . Stokes, Electrolyte solutions, second ed. (Academic Press Inc., New York 1959). [10] R. G. B ates, Ch ern. Revs. 42, 1 (1948) . [11] G. D. Pinching and R. G. Bates, J . Research NBS 37, 311 (1946) RP1749. [12] E. R. Cohen, K. M. Crowe, and J . W. M. DuMond, Fundamental constants of physics (Interscience Publishers Inc., New York, 1957). [13] R. G. Bates, G. D . Pinching, and E. R. Smith, J. Research NBS 45, 418 (1950) RP2153. [14] R. G. Bates, Chimia 14; III (1960).

(Paper 65A3-110)

270

JOURNAL OF RESEARCH of the Nati onal Bureau of Standards-A. Physics and Chemistry Vol. 65A, No. 3, May- June 1961

Publications of the National Bureau of Standards (Including papers in outside journals) Selected Abstracts Irrational power se ri es, M. Newman, P roc. A m. Math. Soc. 11, 699- 702 (Oct. 1960). I t is shown that if a is a real number, g a non-constant poly nomial, then

:s g([na])xn 00

n~O

is a rational fu nction of x if and only if a is a rational numb er. The sa me state ment is proved for the funct ion

Ense mbl e me thod in the theory of irre vers i bility, 11. Zwanzig, J . Chem. Phys. 33, No.5, 1338- 134 1 (Nov. 1960). vVe describe a new formu lat ion of met hod s in trodu ced in the theory of irrevers ibili ty by Van Ha ve a nd Pri,(o;in e, with t he purpose of makinil; their ideas eitsier to und erstan d an d to apply. The main tool in thi s reformu lat ion is the use o f projection operators in t he I-Iilbert s pace of Gibbsian ense mble densities. Projection operators a re used to sep arate [tn e nsemble d ensity into a "relevant" p[trt, needed for the calcu lation of mea n valu es of specifi ed obser vables, and the remaining " irreleva nt" part. The relevant part is shown to satisfy a kinetic equation which is a general ization of Van Hove's " master equation to ge neral order. " Diagram sum mation met hods are not used . The formalism is illustrated by a n ew d erivation of the Pri go~in e-Brou t master eq uation for a classical weak ly interacting system. On the the ory of the critical point of a simpl e fluid, M. S. Green, J . Chem. Ph ys. 33, No.5, 1403- 1409 (Nov. 1960) . The consequences of a new system of in tesral equations for the theory of the critical point are discussed . R easons are given for belie\' ing that the fundam ental assumption of the Ornstein-Zernick e theory about the direct co rrelation function is incorrect. Topological d erivation of the Mayer de nsity seri es for the pressure of an imperfect gas, M . S. Green, J. Math. Ph ys. 1, No .5, 391 - 394 (Sept. - Oct. 1960) . A new derivation of Mayer's classical density expansion for the press ure of an imperfect gas based on a classification of cluster graphs according topological criteria is presented. The classification is a generalization of the classi fi cation of simple trees into trees with centers and trees with bicenters . Collection of ions produced b y a lpha particles in air, Z. Bay and H . H. Seligcr, Phys . R ev. 120, No.1, 141- 143 (Oct. 1, 1960). In the meas urement of the ionization caused by alpha particles in air recombination effects betwee n slowly moving positive and nega tive iOlls (the latter formed by electron attachment to oxygen) have to be considered . The us ual procedure i n s uch meas ure ments is to d etermine Lhe saturaLion current (by extrapolation of r eciprocal current versus reciprocal voltage curves to infini te fi eld strength) accord inoto the Jaffe theory. A p aper by Wingate, Gross a nd Faill~ ~las cast doubt on t he validi ty of this extrapolation technique, III that the a uthors propose a fi eld-llldepend ent. pa rt of the recombination amounting to 3.3 p e rcent at atmospheric press ure in a ir . This p ,·opositl implied t hat a ll previou s meas urements of Wa for air were in error by this amo unt a nd

271

t hat this erro r is a poss ible ca u c fo r· the reportcd diffe rence (3 to 4 p erce nt) betwee n ];V val ues for alpha and beta part icles in a ir. In view of o ur own IV m eas ure me nts we felt compelled to reexamin e this s upposedly fi eld-independe nt part of t he recombination. ApproximaLing the expe ri me ntal conditions of vVin gate, G ,·oss itnd Fai ll a we have not bee n able to reproduce their effect a nd our· ex pe ri ments d e monstrate t he validity of the usual ex trapo lation techniques. Megaro e ntge n dos im etry e mplo yin g photographic film wit hou t processing, \V. L. :vr cLaughlin , Radiation R esearch 13, No.4, 594- 609 (Oct. 1960) . The new photographic method of hi gh-level dosimetry of X- a nd ga mma radiatio n invo lvcs two steps: (1) Large radiation exposures arc given, res ulting in the formation of p ri nt-out image in Lhe sil ver halide e mulsio n layers of ordinar y co mmercial X-ray film s, without requiri ng photographic processing for the e valuation ; (2) Th e unknown expos ure is meas ured by mea ns of a specia l de nsito metric procedure, t he ('x pos ure being related to the net d ensiLy ot the print-out dark e ning on a character istic curve obtained with known cxpos ures. The dens ity readings a re made with a narrow brlnd of red ligh t, obtained by placing a suitable band-pass fi lter betwee n the densitometer lig ht source and the film . Gamma radiation exposures from 2 X 10' to 10 8 roentgens ca n be r ead with a precis ion limi t 01 ± 5 p ercent, under appropriate conditions of densitomctry. The r esponse is rate inde pe nd ent a nd the print-ou t image is stable. The chief limitations in the met hod a rc a considerable d ep cnd ence of r esponse upon radiation energy belo w 0.3 Mev, and the requireme nt of controllin g the temperature d urin g exposure to within ± 10 degrees Cels ius for accurate reac.ings. Vibration-rotation bands of N 20, E. D . Tidwell a nd E. K. Ply ler, J. Opt. Soc. Am. 50, No. 12,717- 720 ( D ec. 1960). About 40 bands of nitrous oxide have been measured with a hi gh r esolution grating spect rometer in the region from 2395 to 35]0 cm- I . Manv first a nd econd hot bands were observed a nd it was po~ssi ble to obtain acc urate-type doubling co nstants. By the use of bands observed in this" ork in conjunction wi th previous work a fairly complete set of v ibrationa l l eH 3- CH - CH 2 • The ratio of propan e to 2,3-dimethylbutan e is abo ut 9 and does not change as the concentration of propene is varied over two

+

o rders of magnitud e. The pTOpan e as well as the 2,3-dimethylbutane mu t therefore be formed by a process which is second order with respect to t he isopropyl radical concentration. Pre paration and thermal stability of tetrakis- (pentatluorophe nyl ) -silane and tris- (pentatluorophenyl) -phosphine, L. A. ' Vall, R. E. Donadio, and ' N. J. Pummer, J . Am. Chem. Soc. 82, No. 18, 4846- 4852 (Sept. 1960). The completely fluorinated organo-metalloid compounds, tetrak is (pe ntafluorophenyl) silane, tris(pentafluorophenyl)phosp hin e, and tris(pentafluorophenyl)phosphine oxide hav e b een prepared from pentafluorophenyl magn esium bromid e a nd the appropriate metalloid chloride. The thermal stabilities of these compounds have been compared with those of other a romatic sub stances. It was found in the case of the phosphine, where coordinating electrons exist on the metalloid atoms, t hat complete fluorine substitution increases its thermal stability and resista nce to oxidation. On the other hand, complete fluorination d ec reases the th ermal sta bility of the silan e. Rate of reaction of nitrogen atoms with ethylene, J . T . H erron, J . Chem. Phys. 33, No. 4, 1273-1274 (Oct. 1960). A mass spect rom etric study has bee n m ad e of t he rate of the r eaction of nitrogen ato ms with et hylene. Th e average value of t he second order rate consta nt ove r the temperature interva l 200 ° C to 330 ° C was 5.8 X 10 10 cm. 3 mole- l sec- l • Surface area determination of kaolinite u sing glycerol ads orption, K. E. Woodside a nd W. C. Ormsby, J . Am. Ceram. Soc. 43, No . 12,671- 672 (Dec. 1960). Som e work has a lready bee n don e on t he application of t he so-called glyce rol rete ntion method in the dete rmination of surfa ce a rea s of clays, in cluding kao li nit es, a we ll as well as othe r solid adsorb ents. The presen t inves tigation compa res the surface a reas of a se ri es of controlled particlesize fraction s of a domestic kaolinite us ing thi s rapid m et hod with t h e more conventional but more laborious ni t roge n adsorption method . R esults showin g good agreement confirm t he work of earli er inv estigators a nd d emon strate t he utility of t he method when app lied to kao lin -type clays . The heat of combustion of dicyanoacetylene , G. T. Armstrong a nd S. M arantz, J . Phys. Chem. 64, 1776- .1 777 (1960). The h eat of combustion of li quid dicya noacety lene (C.N 2) in oxygen to form car bon dioxid e and nitrog en has been measured to be 2078.5 ± 0.7 ki mole- 1 (496 .8 ± 0 .2 kcal mole- I), the indicated uncertain ty being t he sta nd a rd error of the preced in g mean. The standard heat of formation , 61-):0 f298 [C.N,( l) ], is calcu lated to be 120.6 kca l mol e- I. The binding energy at 298 OK of the C.N 2 molecule is calculated to be 783.6 kca l mole- I. Electrodeless passage of direct current through an electrolyte, A. Brenner, J . Elect1·ochem. Soc. 107, No. 12, 968- 973 ( Dec. 1960). An experimental setup is desc rib ed for d irec tly observing the elect rical migration of a dy e i n a conducting sy stem without e lectrodes. Direct current was produced in a contin uolls circui t of elect rolyte, which included the dy e solu tion, by m eans of a transformer and a mec hanical commutator . Condensation coefficient of arsenic trioxide glass, A. B. Bestul and D . E. Black burn, J. Chem. Phys . 33, No.4, 12741275 (Oct. 1960). The maximum rate of vaporization from arsenic trioxide glass at 194 ° C h as been determin ed by measurement of weight loss in vacuum. The results lead to a condensation coefficient of 2.2 X 10- 6 . It has been shown that und etected surface cooling due to the absorption of latent heat of vaporization cannot account for the major part of the d eviation of t his value from unity. The compound BaTiGe30 g, C. R . Robbin s, J. Am. Cerarn. Soc. 43, No. 11 , 610 (Nov . 1960). BaTiGe3 0g is stable from 1132° ± 10 °C to 1235° ± 10 °C. The room temperatu re X-ray powder diffracto meter pattern was ind exed on the basis of a hexago nal un it cell with a= 1l .73A, c= 10.02A a nd c/a= 0.8542 . Th e theoretical d ensity

is 4.54 a nd Z = 6. Th e de crip Lion of Ba TiGe3 0 0 in t he li terature app ar enU y d escrib es a solid solu tion of lita ni .1 in barium tet rage rman ate. At room te mperaLur , B aTiGe30 g is structurall y similar to, but not isost ru ct ural with BaTi i30 o. 'W ithin its temperatu re stabili ty range, BaTiGe30 g is apparently isost ructural with B aTiS i3 0 o, with a~ 6.8A a nd c~ 10 . 04A.

Other NBS Publications Journal of Research, Section 65C, No.2, April- June 1961. 75 cents. An experimental study concerning the pressuri zation a nd stratification of liquid hy drogen, A. F . Schmidt, J . ll. Purcell, 'vV. A. Wilson, and R. V. Smith. T emperature dependence of elastic constants of so me c rmet specimens, S. Spinner. Analog simulation of zo ne melting, H . L . Mason. R esidua l losses in a guard-rin g micrometer-electrod e holder for solid-disk di electr ic s pecimen s, A . E . Scott and William P . Harris. A bolometer mount e ffi cie ncy m easu re me nt techniqu e, G. F . Engen. T elescop e for m eas urement of optic angle o f mica, S. lluthberg. An automatic fringe countin g in te rferometer for usc in t he calibration of lill e s cales, H . D. Cook a nd L. A . Mar zetta. Journal of Research, Sectio n 65D , No.3 , May- Jun e 1961· 70 cents. Propagation studies us in g directio n-findin g Lec hniqu es, E. C. Hayden. Diversity effect.s in long di stance high fr eque ncy rad io pulse propagation, S. A. B owhill . Influe nce of ionosp heric co nditions on the acc uracy of hi gh fr eque ncy direction finding , P . J . D . Cethin g. Phase diff eren ce obse rvation s at spaced aer ia ls and t heir application to di rectio n fi nding, W . C. Ba j n. R esearch at t he National Burea u of Sta ndards a ppl icab le to long-distance location and dir ection-finding proble m , R. Silbers tein . Des ign for spinning goniometer automatic direction findin g, ' V. J . Lindsay a nd D . S . H einl. R esolution characteristics of correlation arrays, 1. W. Lind er. Instrume ntatio n for propagation a nd dir ection-finding measureme nts, E. C. Hay den. Brook e variance classifica tion system for DF bearing , E. M. L. B eale. E s timation of va ri a nces of position lines fro m fixes with unknown target positions, E . M. L . B eale. Statistics of a radio wave diffracted by a random ionosphere, S. A . B owhi ll. Space a na lys is of r a dio sig na l , J . B . m yt h. Effec t of receiver bandwidth on the a mplitude di stribution of VLF atmos pheri c noise, F. F . Fu lto n, Jr. Excitation of VLF and ELF radio waves b y a horizontal magn etic dipole, J . Galejs. Climatic charts and d ata of t he radio r efr active index for the United States and world, B . R. B ean , J . D . I-l orn, and A. M. Ozanich, Jr., NBS Mono. 22 (1960) $2. Units of weight and m eas ure (United States customary a nd metric) definitions a nd t a bles of equiv alents, NBS Misc . Pub!. 233 (1960) 40 cents. R eport of the 45th national confer enc e on weights and measures 1960, NBS Misc. Pub!. 235 (1960) 75 cen ts. Standard fr equencies a nd tim e signals frOIll NBS statio113 WWVand WWVE, N BS Misc. Pub!. 236 (1960) 10 cents. Research highlights of the National Burea u o f Standards, Annual Report, fiscal year 1960, ~BS Misc. Pu b!. 237 (1960) 65 cents. R eport of t he Internation al Commission on rad iological units and meas urem ents (rcRU) J959, NBS Handb. I-l78 (1961) 65 cents. Supplementary world maps of F2 critical fr equ enc ies an d maximum usable fr equ ency factors, D. H. Zac harisen, NBS T N2-2 (PB151361- 2) (1960) $3.50.

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Vapor pressures of organic compounds in the range below one millimeter of mercury, E . E. Hughes and S. G. Lias, NBS TN70 (PB161571 ) (1960) 75 cents . Quarterly radio noise data- June, July, August 1960, W . Q. Crichlow, R. D. Di3ney, and M. A. Jenkins, NBS TNl8-7 (PBl51377- 7) (1960) $1.75. VHF radio propagation data for Cedar Rapids-Sterling, Anchorage-Barrow, and Fargo- Churchill test paths April 1951 thro ugh Ju ne 1958, G . R. Sugar and K. W. Sullivan, NBS TN79 (PB 161580) (1960) $4.00. Bibliography of tropospheric radio wave scattering, R. L. Abbott, NBS TN80 (PB 16158l) (1960) $2.25. A survey of spread-f, F . N. Glover, NBS TN82 (PB161583) (1960) $1.75 . The NBS meteor-burst propagation project-a progress report, C. E. Hornback, L. D. Breyfogle, and G. R. Sugar, NBS TN86 (PB161587) (1960) $1.25. A theoretical study of sporadic-E str ucture in the light of radio measurements, K. Tao, NBS TN87 (PB161588) (1961 ) $1.25 . Flexural strength of spe~imens prepared from several uranium dioxide powders; its dependency on porosity and grain size and t he influence of additions of titania, F. P. Knudsen , N. S. Parker, and M. D . Burdick, J . Am. Ceram. Soc. 43, No. 12, 641- 647 (Dec. 1960) . Correlation of an auroral arc with a subvisible monochromatic 6300 A arc with outer-zone radiation on November 28, 1959, B. J. O'Brien, J . A. Van Allen, F. E. Roach, and C. W . Gartlein, J . Geophys. R esearch 65, No.9, 2759- 2766 (Sept. 1960). Report on the standardization of pH and related ter minolo gy, R. G. Bates and E. A. Guggenheim, Intern. Union Pure and Appl. Chern. 1, No.1, 163- 168 (1960). Regulated power supply for instruments, W. V. Loebenstein , Electronics 33, No. 48, 132 (Nov. 1960). Some ceramic dielectrics with a very low temperature coefficient of capacitance, S. Marzullo and E. N. Bunting, J. Am. Ceram. Soc. 43, No. 11, 609, (Nov. 1960). The sample, the procedure, and the laboratory, VV. J. Youden, Anal. Chem. 32, No. 13, 23A- 37A (Dec. 1960) . Residual arc spectra of seventy elements diluted in copper, C. H. Corliss, IV. F. Meggers, and B. F. Scribner, Book, Colloquium spectroscopicum internationale VIII, 119- 121 (1959). The relation of h max F2 to M(3000) F2 and HpF2, J. W. Wright and R. E. McDuffie, J . Radio Research Lab. 7, No. 32, 409-420 (Ju ly 1960) . 8-quinolinol precipitation of t he elements, J. 1. Hoffman, Chem. Anal. 49, No.4, 126 (Dec. 1960). A test of a procedure for easy estimation of representative monthly electron density profiles for the ionosphere, J . W. Wright, J. Geophys. Research 65, No. 10, 3215-3217 (Oct . 1960). A method for efficiently providing low temperature liquids on a large scale to an accelerated ex perimental program, A. K . Stober, Proc. 10th I ntern. Congress of Refrigeration, Copenhagen, D enmark 1, No. 1, 17- 18 (Pergamon Press Ltd., London, England, 1959). Seasonal variations in the twi light enhancement of [01] 5577, L. R. Megill, P. M. J amnick and J . E. Cr uz, J. Atmospheric and Terrest. Phys. 18, 309-314 (Aug. 1960). Synthetic mica, A. V. Valkenburg, Book, Encydopedia of Chemical T echnology, p. 480-487 (I nterscience Encyclopedia, Inc., I'Iew York, N. Y., 1960).

Precipitation of the elements on addit ion of aqueous ammonia to their clear solution, J . 1. Hoffman, Chern. Anal. 49, No.3, 94 (Sept. 1960). Low scatter high current gas target for D-D neutrons, A. C. B. Richardson, Rev. Sci. Inst. :U, No. 11 , 1202-1203 (Nov. 1960) . Evaluation of resistance strain gages at elevated temperatures, R. L. Bloss, Am. Soc. T esting Materials Proc. 1, No.1, 9- 15 (Jan. 1961 ). Errors in dielectric measurements due to a sample insertion hole in a cavity, A. J. Estine, and H. E. Bussey, IRE-Trans. Microwave Theory and T ech. MTT- 8, No.6, 650-653 (Nov. 1960). Determination of pentosans. Interlaboratory comparison of the aniline acetate, orcinol, and bromination methods, W. K. Wilson and J. Mandel, Tappi 43, No. 12, 998-1004 (Dec. 1960) . A research for geomagnetic singular days, C. Warwick, T. Pohrte, and N. MacDonald, J. Geophys. R esearch 65, No. 9, 3013- 3015 (Sept. 1960). Letter to editor of Revue Des Materiaux (first), E. S. Newman and H. A. Berman, Revue Des Materiaux C, No. 540, 231 Dec. 1, 1960). Geomagnetic storms and the space around the earth, S. Chapman, Nature 187, No. 4740, 824-827 (Sept. 3, 1960). Some implications of slant-E., E. K . Smith and R. W. Knecht, Polar Atmosphere Symp., Part 2, Ionospheric Section, Oslo, Norway, July 2-8, 1956, p. 195-204 (Pergamon Press, Inc., New York, N.Y., 1957) . Experimental investigation of creep deflection of extr uded and riv eted I- beams, L. Mordfin and N. Halsey, NASA Tech. Note D - 662 (December 1960). The measurement of thermal conductivity, D . C. Ginnings, Book, Thermoelectric materials and device~, edited by 1. B. Cadoff and E . Miller. Chapter 8 113-132 (Rheinhold Publishing Corporation, New York, N. Y., 1960). Programming for a closed-loop, manned-machine combined system, D. C. Friedman, Proc. Combined Analog-Digital Computer Systems Symp ., December 16 and 17, 1960, Philadelphia, Pa., 12th Article (Dec. 1960). Analytical study of creep deflection of structural beams, L. Mordfin, NASA T e ch. Note D-661 (Dec. 1960). Evaluation of ball bearing separator materials operating submerged in liquid nitrogen, W . A. Wilson, K. B. Martin, J. A. Brennan, and B. W. Birmingham, ASLE. ASME; Lubrication Conf., October 17- 19, 1960 (Boston, Mass.), Am. Soc. Lubrication Engrs. preprint No. 60 LC-4 (1960). Aircraft storage batteries, W. J. Hamer, AlEE and Am. Inst. Elec. Engl'. Trans. 79, Pt. II, 1- 11 (Sept. 1960). Stress-strain relationships in yarns subjected to rapid impact loading. Part VI: Velocities of strain waves resulting from impact, J. C. Smith, J. M. Blanford, and H. F. Schiefer, Textile Research J . 30, No . 10, 752- 760 (Oct. 1960) . The centennial of spectrochemistry, VV. F. Meggers, J . L Tech, J. Opt. Soc. Am. 50, No. 11, 1035- 1038 (Nov. 1960).

Publications faT which a price is indicated (excep t for NBS Technical Notes) are available only from the Superintendent of Documents, U.S. Government Printing Office, Washington 25, D.C. (foreign postage, one-fourth additional). Technical Notes are available only from the Office of Technical SerVices, U.S. Department Of Commerce, Washington £5, D .C. (order by PB number). Reprints from outside journals aoo the NBS Journal Of Research may often be obtained directly from the authors.

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