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tion of a n excess amount of potassium iodate and potassium iodide, which releases an amount of iodine equivalent t o t h e excess acid. T h e released iodine is determined by titrating with approximately 0.0007 S sodium thiosulfate, using starch as an indicator. This procedure retains the theoretical and practical advantages of the methods where calcium oxalate is converted t o calcium carbonate and combines with it t h e sensitivity of iodometric titrations. All solutions are standardized against t h e relatirely stable 0.01 S hydrochloric acid uqed.
Literature Cited (1) Clark, IT. M , "Determination of Hydrogen Ions". 3rd ed., Baltimore. Williams d Wilkins. 1928
VOL. 12, NO. 2
(2) Dumaaert, C.. Bzcll. SOC. chim. b i d . , 20, 1405 (1938). (3) Fiske, C. H . , and .%dams. E. T.. J . A m . Chem. Soc., 53, 2498 (1931). (4) Kolthoff, I. h l . . and Sandell. E. B., "Texthook of Quantitative Inorganic Analysis", pp. 326-31, 589, 592, New York, Macmillan Co.. 1936. ( 5 ) Lebermann. F., .Uiinch. med. Tl'ochschr.,71, 1392 (1924) ; Chem. Zejatr.. 1, 139 (1925). (6) Nordbii, R., Riochem. Z., 246, 460 (1932). (7) Sieve, S.h., I h i d . . 278, 442 (1935). ( 8 ) Sobel. A. E., Pearl, A . , Gerchick, E., and Kramer. B.. J . Biol. Chem.. 118, 47 (1937). (91 Sohel. A. E., and Yklersky, S., Ibid., 122, 665 (1938). (10) Sobel, .1.E.. and Sohel, B. A , , I b i d . , 129, 721 (1939). (11) Trevan, J., and Bainhridge, H. W., Biochem. J . , 20, 423 (1926). (12) Washburn. 91. L . , and Shear, M. J., J . Biol. Chem., 99, 21 (1932).
An Improved Iodine Apparatus F. X. GASSNER Colorado Experiment Station, Colorado S t a t e College, Fort Collins, Colo.
F
OR the determination of traces of iodine in feedstuffs
and similar material, t h e method of Karns (1) as modified by von Kolnit'z and Remington ( 2 ) seems t o b e the most
suitable procedure available from the standpoint of accuracy simplicity, and versatility. T h e metal torch designed tiy the lat8terauthors has certain disadrantages, and several changes have been made in t h e material, design, and construction of this apparatus which are heliered t o he distinct improvements. To avoid the inconvenience of keeping the brass lacquered to prevent contamination of the sample by corrosion, the torch is constructed entirely of special resistant stainless steel, Allegheny chrome-nickel alloy 18-8. A further advantage of the stainless steel is its l o x heat conductivity. The four oxygen connectors are replaced by a single inlet tube, which supplies oxygen t o the stainless steel jets through a built-in equalizing chamber. The outlet tube is also of stainless steel, since the glass tube sometimes cracked from the heat. All joints are soldered with special heat-resistant, corrosion-resistant material (special stainless steel solder furnished by ,J. T . Ryerson & Son, Inc., Chicago, Ill.). To eliminate the danger of explosion which occurred when cinders from high-ash samples clogged the constricted tube tip in the first Milligan wash bottle, a simple trap is attached in the manner shovn in the illustration. The prongs which hold the sample are made of Ferralloy, a material especially designed t o resist oxidation a t high temperatures. The torch is reduced in length by 15 cm. (6 inches), which was found to be a distinct, advantage. It is, hon-ever, sufficientll- long to permit the burning of feed samples up to 30 cm. (12 inches) in length. The measurements used in construction of this torch conform otherwise to those given by von Kolnitz and Remington
(a).
The upper part of the torch is corered either b y a 1000-cc. widemouthed ErIenmeyer flask or a 1-liter ivide-mouthed extraction flask with vial-type neck, The use of the latter flask resulted in less breakage and more rapid and more complete combustion. Discoloration of this part of the torch after long usage may be remedied by immersing it in a solution of concentrated nitric acid 25 per cent, hydrofluoric acid 3 per cent, and viater 72 per cent, and heating the mixture to '70" C. for 5 minutes. Care should be taken not to immerse the torch too far in the pickle. The solution must not come in contact with any soldered joint. T h e torch has also been found useful in determining the iodine content of biological material such as thyroid glands.
-4cknowledgment T h e changes herein described were made in collaboration with A. R. Patton.
Literature Cited (1) Karns, G. M . , IND. ENG.CHEY.,Anal. E d . , 4, 299-300 (1932). (2) Kolnita, H. von, and Remington, R. E.. Ihid.. 5, 38-9 (1933).
