162.
No powder data have been reported in the literature.
Thorium Orthophosphate, Th,(PO,),
JAGDISH SHANKAR and
P.
X-RAYDIFFRACTION DAT-4. a = 10.55 A., b = 10.66 A., c = 8.80 A. B = 1106’41’.
G. KHUBCHANDANI
Chemistry Division, Atomic Energy Establishment (Trombay), Bombay, India
X-Ray Powder Diffraction Data for Thorium Orthophosphate Irel.
8 45 5 31 5 06 4.54 4.23 3.86 3.68 3.47
2.76 2.68 2.55 27 more
8 47 5 32 5 04 4 56 4 23 3 87 3.66 3.49
2.76 2.66 2.54
VV.V S S
V.IV. V.S. T-.K. V.W.
s.
W. V.W. V.W.
001 020 200 021 002 201 220 3o i
132 040 041
2.51 2.34 2.29 2.13 2.08 2.02 1.98 1.95 1.94 1.89 1.85 1.82 1.79 1.78 1.75 1.73
2.51 2.33 2.28 2.12 2.08 2.02 1.98 1.95 1.94 1.88 1.84 1.82 1.79 1.77 1.75 1.73
M.S.
S.
hl.S. V.W. K.
V.W. V.TT.
w.
IT. IT.
IT. IT.
IV .
w.
“
hkl 222
302
h1.S. h1.S.
Formula Weights. 2. Density. 3.85, 3.77 (calculated). Crystal System. Monoclinic. S m c e G r o w . Possiblv P2, Pm, or P2im. T h e x-ray powder diffraction data were obtained using a camera 143.2 mm. in diameter and copper K radiation with nickel filter.
420 050 (004) 014 500 510 242 402 529 343 35 i 350 060 169 161
indexable lines w r e observed.
I
ACKNOWLEDGMENT
Thorium orthophosphate was prepared b y Y. W. Gokhale of this establishment, t o whom grateful thanks are due. LITERATURE CITED
(1) Peiser, H. S., Rooksby, H. P., Wilson, A. J. C., “X-Ray Diffraction by
Polycrystalline Materials,’’ Institute of Physics, London, 1955.
HoRIuhf orthophosphate when prerpared from a solution of the thorium salt is obtained as a colloidal gel. On being heated t o 1000” C. in a n atmos-
phere of nitrogen, the gel yields a polycrystalline mass. The crystal parameters were deduced b y indexing a powder photograph b y Ito’s method ( I ) .
CONTRIBUTIONS of Crystallographic Data to be published in ANALYTICALCHEMISTRY should be sent to W. C. McCrone, 500 East 33rd St., Chicago 16, Ill.
Formamide as an Extraction Solvent in Karl Fischer Method for Determining Moisture in Lactose and Maltose SIR: In the recent review article on food (5), a reference was given (2) which pointed out that the Karl Fischer moisture method applied to ordinary skim or whole milk powders does not include all of the water of crystallization of the lactose. Previously (6), i t has been reported that as a result of the insolubility of maltose and lactose in both methanol and the Karl Fischer reagent, these materials can be determined only after preliminary extraction, and when the materials are finely ground. Formamide has been used t o replace methanol as the extraction solvent for the determination of moisture in some food products, including cake mixes containing dried milk solids (3, 4). As lactose and maltose are soluble in formamide, it appeared to be a superior extraction solvent when these sugars, or perhaps products containing them, are t o be analyzed for moisture by the Karl Fischer method. Using the procedure previously de-
scribed (4, we have obtained the following results and compared them with a vacuum oven method ( 1 ) . The sugars were the monohydrates of analytical reagent grade lactose and maltose. X o stirring time was required and the samples were titrated as soon as they were dissolved.
It can be concluded that formamide is a practical extraction solvent for use in the Karl Fischer method, to determine both the water of crystallization and adsorbed water in lactose and maltose. Formamide might readily be adapted for use in products that contain these sugars. LITERATURE CITED
Comparison of Fischer and Oven Methods
Material Lactoseo Maltose“
a
% Moisture Fischer Oven 5.05 5.05 5.09
5.06 5.02 5.01
5.63 5.59 5.61
5 58 5.64 5.57
Calculated % ’ H20 for monohydrates
of lactose and maltose = 5.00%.
(1) Assoc. Offic. Agr. Chemists, “Methods of Analysis,” 8th ed., p. 265, 1955. (2) Kumetat, K., Australzan J . Dairy Technol. 10, 114 (1955). (3) McComb, E. A., NcCready, R. M., J . Assoc. O ~ CA.g r . Chemists 35, 437 (1952 ). (4) McComb, E. A., Wright, H. M., Food Technol. 8 , 73 (1954). (5) Von Loesecke, H. IT., ANAL. CHEM. 29, 647 (1957). (6) Zimmermann, A., Fette u. Seifen 46, 446 (1939).
ELIZABETH A. MCCOMB Western Regional Research Laboratory, Albany 10, Calif. VOL. 29, NO. 9, SEPTEMBER 1957
1375
New Color Test for Selenium SIR: Selenium and its compounds are notorious for their toxicity. As the industrial use of selenium and its derivatives has been mushrooming, the possibility of air contamination by these chemicals has suggested the necessity for a stable, sensitive, and specific test for selenium, which should be capable of adaptation to quantitative work. As elemental selenium, selenides, selenites, and selenates are readily converted to selenous acid by a n oxidizing agent such as nitric acid or hydrogen peroxide in the presence of concentrated hydrochloric acid, procedures for the detection or determination of seleneous acid can be applied to practically any inorganic selenium compound. Selenous acid can be detected by reaction with iodides in acid solution ( 7 ) , with thiourea in acid solution (2) through the formation of a red precipitate of selenium, or with asymmetric diphenylhydrazine (4). The hydrazine is oxidized to a mixture of compounds which have an unstable red-violet color. -4nother test for selenous acid involves oxidation of pyrrole in phosphoric acid solution to give a mixture of blue-green dyes of unknown constitution (9). The disadvantages of redox procedures for the detection and determination of selenium have been mentioned by Cheng (I). A brown mixture of compounds of uncertain structure is formed b y the reaction between selenites in acetic acid solution and 1,8naphthalenediamine (3). Hoste (5, 6) and Cheng ( I ) have also shown that 3,3'-diaminobenzidine reacts with selenous acid to form a light yellow 5,5'dipiaselenol. This nonredox reaction is Fpecific for selenous acid and has been used by these authors for the determination of selenium. The dipiaselenole has a n-ave length maximum a t 347 to 349 mp in aqueous solution. Although red, blue. or green colors are not too common in spot test malysis, a yellow color interferes in many organic reactions. Because so many organic compounds absorb in the ultraviolet and a fairly large number near 400 mp>a compound absorbing in this range would be more difFicult to determine because of the greater possibility of interference. The author has found that the colorless 4 - dimethylamino - 1,2 - phenylenediamine and 4 - methylthio - 1,2phenylenediamine react with selenous acid to give stable bright red and blue1376
ANALYTICAL CHEMISTRY
purple colors, respectively, in appropriate media. The preparation of the diamine salts and their derived piaselenoles has been described (8). Both of the piaselenoles are stable, fairly insoluble in water, and very soluble in ether, alcohol, and benzene. The bright red color formed in the spot test for selenous acid with 4-dimethylamino1,2-phenylenediamine dihydrochloride is due to the following reaction:
, , ,A
substituted for 3,3'-diaminobenzidine, with minor modifications in the procedures of Hoste and Gillis (6) or Cheng (1) for the quantitative determination of selenium. EXPERIMENTAL
Ten microliters of the aqueous or alcoholic test solution containing selenous acid was mixed in a microtube with 20 p1. of a 0.5% aqueous solution of 4methylthio - 1,2 - phenylenediamine
449 mp
As this piaselenole has its wave length maximum at 449 nip in alcoholic solution and 503 mp in approximately 1 N hydrochloric acid solution, the latter medium is preferable for the detection or determination of selenium. On the other hand, the blue-purple color obtained in the reaction of selenous acid with 4 - methylthio - 1,2 - phenylenediamine hydrochloride is caused b y the presence of the quantitatively formed, stable, dicationic dye:
hydrochloride. If kept in the refrigerator, the latter solution is stable at least 2 weeks. The other diamine is also stable for 2 weeks. After the solutions mere mixed and allowed to stand for 5 minutes, the drop mas evaporated under a vacuum.
5 - Methylthio - 2,1,3 - benzoselenadiazole or 5-methylthiopiaselenole is yellow in 95y0 ethyl alcohol, A,, 390 mp. It forms a red monocationic salt in 50% sulfuric acid, A,, 448 mp. T o obtain the highly colored dicationic salt, sulfuric acid has to be the solvent. Either of the two reagents could probably be advantageously
sary, for then the solvent composition is readily controlled-for example, 5methylthiopiaselenole formed in one procedure is blue-purple in concentrated sulfuric acid (the dicationic salt) and red in 50y0 sulfuric acid (monocationic salt). If the test drop were not thoroughly dried, this solvent remainder could dilute the sulfuric acid enough to
Drying in a vacuum is not necessary. but evaporation under a vacuum speeded up the operation. Drying of the sample was believed to be necee-
