V O L U M E 23, NO. 4, A P R I L 1 9 5 1
675 buret increment corrections t o the observed diffusions current8 are negligible. Results obtained by this procedure are shown in Table I. CALCULATION
V X M X 30.98 X 100
s
%P= where
V M S
= volume of uranyl acetate solution = molarity of uranyl acetate solution = weight of sample in milligrams
The uranyl acetate solution is standardized according to the described procedure except t h a t 5 ml. of 0.001 M potassium dibydrogen phosphate and 2 ml. of water are substituted for the neutral solution of phosphate and the two 1-ml. portions of wash water. LITERATURE CITED (1) Kolthoff, I. M., and Cohn, Gunther, IND.ENQ.CHEM.,ANAL ED., 14, 412 (1942).
43. Sodium Stannate, Na,Sn(OH), Contributed by JOHN KRC, JR.. Armour Research Foundation, Illinois Institute of Teohnology, Chicago 16, 111.
OOD crystals of sodium stannate ( 1 ) can be obtained on
B
G macro sesle from water solutions after prolonged evapora-
tion. C~yatalsprepared on a microscope slide are extremely small and poorly formed. Other investigators have reported sodium stannate as crystallizing a8 rhombohedra and ditrigonal scalenohedra (2, 8).
CRYSTAL MORPHOLOGY Crystal System. Hexagonal. Form and Habit. Plates lying on basal pina_eoid, 0001, and showing firsborder hexagonal bipyamics, [ 10111, and o c w sianally firstorder hexagonal prisms, (1010). Asia1 Ratio. a:c = 1:2.373 (hexagonal).
Figore 2.
Crystals of Sodium Stannate Principal Lines
d
I/II
d
otii
~ n t e r i a c i a h~ g l e s (polar).
iiotAiioi
= 69' 56'.
Figure 1. Orthographic Projection of Typical Crystal of Sodium Stannate
X-RAYDIFFRACTION DATASpace Group. C:i-R3
@).
=
40' 8';
iioinaooi
L
ANALYTICAL CHEMISTRY
676 Cell Dimensions. Hexagonal. a = 5.956 A , , c = 14.13 A4.; a = 5.95 A,, c = 14.17 A. ( 2 ) . Rhombohedral. a = 5.832 A,, CY = 61” 24‘; a = 5.84 A , , a = 61.2’ (2). b 1
L
Formula Weights per Cell.
IO\
Hexagonal 3.
Rhombohedral
(*I.
Formula Weight. 266.7. Density. 3.00 (pycnometer) : 3.06 (x-ray). OPTICAL PROPERTIES Refractive Indexes (5893 -4.; 25” C.). w = 1.568 * 0.002. E = 1.582 * 0.002. Sign of Double Refraction. Positivc. h6lecular Refraction ( R )(5893 A.; 25” .\”/;?; = 1.573 * 0.002. n (av.) = 1.576 calculated from Gladstone and Dale formula. R (calcd.) = 29.3. R (obsd.) = 29.3. FUSIOX DATA. Sodium stannate undergoes gradual decomposition a t temperatures well above 200” (’. Decomposition occurs
e.),
without melting, The rate of decomposition is very d o w at. about 240” C. and is rapid a t ahout 275” C. and above. ACKNOWLEDGMENT
I t is a pleasure to acknowledge the assistance of Irene (’orvin in the determination of powder x-ray diffraction spacings and intensities. LITERATURE CITED
(1) Belluci, I., and Parravano, N., Atti accad. Lincei, (5) 1311,307 (1904); Z.anorg. C‘hem., 45, 142 (1907). (2) Bjorling, C. O., A r k i a Kpmi, M i n e r d . Geol., 15B, No. 2, 1-0 (1941). (3) Marignac, J. C. G. de. Ann. mines, ( 5 ) 15, 278 (1859). CONTRIBUTIONS of crystallographic data for this section should be sent t o Walter C. McCrone, .inalytical Section, Arniour Research Foundation of Illinois Institute of Technology, Chicago 16, Ill.
Second Pittsburgh Conference on Analytical and Applied Spectroscopy
T
HE second annual conference, which was a joint meeting
of the Analytical Division of the Pittsburgh Section of the AMERICANCHEXICAL SOCIETYand the Spectrosropy Society of Pittsburgh, was held on March 5, 6, and 7, 1951, at the William Penn Hotel. The significance of this meeting was attested by the regist’ration, which exceeded 950 by the second morning of the conference. Three days are barely enough, at the present time, to accommodate the wealth of addresses and technical papers. T h e first two annual Pittsburgh .4nalytical SympoPia of 1946 and 194i were one-day affairs. The joint session on Monday morning was welcomed by Chairman It. G. Russell of the Analytical Group and Chairman J. J. NcGovern of the Spectroscopic Society. Walter J. Murphy, Editor of ANALYTICAL CHEMISTRY, made well chosen remarks on the phenomenal growth of analytical chemistry, the widening scope of t,he journal, and the growing importance of analytical symposia held annually in various parts of the country. The session n-as honored by the presence of BCS President N. Howell Furman, who presented an excellent paper on “Electrochemical Methods of Analysis with Emphasis on Coulometric Titrations.” Furman’s gracious tribute to the ingenuity and skill of his younger associates in the work, however sincere, could not conceal the infallible touch of a master analyst. G. H. Dieke of Johns Hopkins University, ih discussing “Fundamental Considerations for a Practicing Spectroscopist,” outlined the wealth of information which can be obtained from arc or spark sources when photoelectric-oscillographic observations of the source are made. When these are supplemented by electronic gating techniques, one can delineate the time-history of the excitation process. One gained the impression from his interesting results, that however useful empirical emission spectroscopy may be, much of wh:it has been done spectrochemically before these techniques were evolved could be entitled “The Light T h a t Failed.” 11. G. AIellon, Purdue University, spoke on “Analytical .lutomat,ons” and pointed out the increasing trend to make anal~-ticiJoperations entirely automatic. This often becomes mandatory when practically all other operations in a production line have been mechanized. Mellon emphasized the value of the “unit, operat,ions” approach in t.he classification of methods, and classified the essential analytical operations which are the necessary precursors of any automatic system. Additional highlights were the testimonial dinner to astrophysicist and spectroscopist Keivin Burns, and the conference dinner, addressed by Paul D. Foote of Gulf Research & Development Co. Seventeen instrument and apparatus companies exhibited equipment, and an impressive array of reference books and monographs relating t,o the two fields was on display in the registration lounge.
hbstracts of the t,echnical papers follow: Electrochemical Methods of Analysis. Coulometric Titrations. N. HOWELL FURMAN, Princeton University. Some of the chief lines of recent advance in the application of electrochemical methods of analysis were briefly surveyed. A detailed account of local experience with various modifications of the coulometric titration tnethod was presented. The latter method appears to offer decided advantages in microgram titrations of various substances. Potentiometric rather than aniperometric deGices for the estimation of end-points have been found to be advantageous both in the macro and micro fields, whereas the amperometric technique gives excellent service in an intermediate range. Fundamental Considerations for a Practicing Spectroscopist. G. H. D I E K EJohns , Hopkin3 Univewity. Purdue University. Analytical Automatons. M. G. MELLON, In the drive for mass production in industry one of the phenomenal developments for some decades has been the automatizing of both single- and multiple-unit operations. Whatever the reasons for the changes, and their economic and social effects, the process continues unabated. Quantitative chemical analysis has heen slowly but steadily yielding to this trend, until today we h a w many examples, especially in industry, of processes operating on an automatic basis. The devices range from relatively simple equipment which performs a single operation, such as sampling, to recording instruments which make a continuous graph of the amount of a desired constituent in a passing stream of material. The latter type is illustrated by recorders used in power plants for determining carbon dioxide in stack gas. More striking, although iiot so nearly completely automatic. are the new eniission spectrometers deaigned to indicate directly and simultaneously the percentages of nearly a dozen constituents. The ultimate in industrial mechanization is the integration of such a device with control equipment for maintaining some given chemical composition. .ittention was directed to basic operations of chemical analysis which have been found to he automatizable, and t o examples of means which has heen adapted to this purpose. Since increasing autoniatization seems likely, some possibilities and unsolved problems were reviewed briefly. The Electronic Theory of Acids and Bases. W. F. LVDER, Northeastern Cniversity. Recent experiments suggested by the electronic theory of acids and bases are reported, including: reactions of metals with thionyl chloride in the presence of acidic catalysts such as aluminum chloride, ferric chloride. and stannic chloride. Preliminary qualitative investigations of the effect of similar acids on various indicators in the four solvents, benzene, chlorobenzene. ethylene chloride, and thionyl rhloride, and conductometric titrations in thionyl chloride. Polarography in Nonaqueous Solvents.
S . RIDIN,Purdue University.
T H O M DE ~ S TRIESA N D
A study has been made of the polarographic reduction of nitro derivatives of ethane, propane, butane, and dinitro derivatives of propane and pentane. The supporting electrolyte was lithium chloride in eight different solvents-methanol, ethanol, propanol, butanol, ethylene glycol, and glycerol, and solutions of some of these with benzene or dioxane. The diffusion current was found to he inversely proportional to the square root of the viscosity of the solvents. The number of electrons involved in the reduction has been calculated with the Ilkovii. equation and confirmed by using Lingane’s method of coulometric analysis. The reduction of nitrobutane becomes more difficult and the waves more drawn out as the methanol concentration is decreased on methanol-dioxane mixtures and the
