Mar., 3,922
T H E JOURNAL OF IXDUSTRIAL A N D ENGINEERING CHEMISTRY
209
TABLE 11-COMPARISONO F OFFICIALA N D HYDRAZINE DISTILLATION METHODS
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ARSENICOXIDE FOUND, GRAMS-------Titrated Titrated Titrated after after Method of Titrated after 1 Day 2 Days No. Material Analvzed Distillation Immediatelv 4 Hrs. 0.1241 0.1239 Calcium arsenate Official 0.1248 15794 0.1281 0.1281 .Hydrazine 0.1251 .... 0,1237 0.1234 Calcium arsenate Official 0.1242 15515 0.1246 0.1246 Hydrazine 0.1246 .... .... 0.1287 0.1287 Calcium arsenate Official 0.1287 15468’ 0.1293 0.1293 Hydrazine 0.1293 .... 0.1219 Calcium arsenate Official 0.1219 .... 0.1219 157921 0.1222 0.1222 Hydrazine 0,1222 .... 0.1256 Calcium arsenate Official 0.1281 0.1270 0.1250 T 1127 0.1281 0.1281 Hvdrazine 0.1281 .... 0.1193 Calcium arsenate Official 0.1241 0.1231 0.1210 T 1128 Hydrazine 0,1241 .... 0.1241 0.1241 0.1089 0.1067 0.1053 Calcium arsenate Official 0,1099 T 1776 Hydrazine 0.1101 .... 0.1101 0.1101 0.1188 0.1179 0.1175 Lead arsenate Official 0.1188 16333 0.1188 0.1188 Hvdrazine 0.1188 0.1188 1 Contained only a trace of nitrates by phenolsulfonic acid test.
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hfETHODg REAGEKTS. Starch Indicator-Mix about 0.5 g. of finely powdered potato starch with cold water to A thin paste; pour into about 100 CC. of boiling water, stirring constantly, and discontinue heating immediately after the paste is added. Standard Arsenic Trioxide Solution-Dissolve 2 g. of pure arsenic trioxide in a beaker by boiling with about 150 to 200 cc. of water containing 10 cc. of concentrated sulfuric acid, cool, transfer to a 500-cc. graduated flask, and dilute to the mark. Standard Iodine Solution-Prepare an approximately 0.05 N solution as follows: Mix intimately 6.35 g. of pure iodine with twice its weight of pure potassium iodide. Dissolve in a small amount of water, filter, and dilute the filtrate to 1 liter in a graduated flask. Standardize as follows: Pipet 50 cc. of the arsenic trioxide solution into an Erlenmeyer flask, dilute to about 200 cc., neutralize with sodium bicarbonate, add 4 to 5 g. in excess and add the standard iodine solution from a buret, shaking the flask continuously, until the yellow color disappears slowly from the solution, then add 5 cc. of the starch indicator and continue adding the iodine solution drop by drop until the permanent blue color is obtained. Calculate the value of the standard iodine solution in terms of arsenic trioxide and arsenic pentoxide. Standard Bromate Solution-Dissolve 1.688 g. of pure potassium bromate in water and dilute to 1 liter. Standardize as follows: Pipet 25 cc. of the arsenic trioxide solution into an Erlenmeyer flask, add 15 cc. of concentrated hydrochloric acid, dilute to 100 cc., heat to 90’ C., and titrate with the bromate solution, using methyl orange as indicator. The indicator should not be added until near the end of the titration, and the flask should be rotated continuously in order to avoid any local excess of the bromate solution. The end-point is shown by a change from red to colorless, and the bromate should be added very cautiously when approaching the end of the titration. Hydrazine Suljate and Sodium Bromide Solution-Dissolve 20 g. of hydrazine sulfate and 20 g. of sodium bromide in 1 liter of dilute (1 : 4) hydrochloric acid. DETERMINATION-weigh accurately an amount of the sample containing the equivalent of not more than 0.6 g. of arsenic pentoxide and transfer to a distilling flask. Add 50 cc. of the solution of hydrazine sulfate and sodium bromide and close the flask with a stopper through which passes the stem of a dropping funnel. Connect to a well-cooled condenser, the delivery end of which is attached to the syfitem of flasks described by Roark and McDonnel1,s omitting the h!!ODIFIED
0 In working out the details of this method it was assumed that commercial calcium or lead arsenates would never contain nitrates in excess of 5 per cent NnO6. I n the case of mixtures containing morethan this amount, the method may require some modification.
Titrated after 9 Days 0.1231 0.1251 0.1231 0.1246 0.1287 0.1293 0.1219 0.1222 0.1237 0.1281 0.1172 0.1241 0.1048 0.1101
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-PROPERTIES OF DISTILLATESBleaching Action on Methyl Color Orange a t 90’ C. None Marked Kone None None Marked None None None None None None None None None None Yellow Marked None None Yellow Marked h’one None Yellow Marked None None Very light yellon. Slight None hTone
third flask. Boil for 2 or 3 inin., then add 100 cc. of concentrated hydrochloric acid by means of the dropping funnel and distil until the volume in the distilling flask is reduced t o about 40 cc.; add an additional 50 cc. of concentrated hydrochloric acid and continue the distillation until the contents of the flask are again reduced to about 40 cc. Wash down the condenser, transfer the contents of the receiving flasks to a 1-liter graduated flask, make to volume, and mix thoroughly. Pipet a 200-cc. aliquot to a 500-cc. Erlenmeyer flask, nearly neutralize with sodium hydroxide, finish the neutralization with sodium bicarbonate, add 4 to 5 g. in excess and titrate with standard iodine solution, using starch solution as indicator; or to the 200-cc. aliquot add 10 cc. of concentrated hydrochloric acid and titrate with standard bromate solution, as previously described in this paper. With a sample equivalent to 0.6 g. of arsenic pentoxide, practically all of the arsenic is distilled over in the first 50 cc. of the distillate, which is a much more rapid volatilization than that which occurs in the official distillation method. A total distillate of 150 cc. is sufficient to insure complete distillation of the arsenic. The method has been applied to the analysis of commercial samples of calcium arsenate, lead arsenate, and other arsenical insecticides containing nitrates, with most satisfactory results in all cases. Table I1 shows the results obtained by the “official” and by the modified method on commercial samples of lead and calcium arsenates containing nitrates. I n the case of the calcium arsenates 1.5 g. of sample were taken for the determination and 2 g. in the case of lead arsenates. The titrations mere made on aliquot portions reprcsenting 0.3 and 0.4 g. of sample, respectively. The figures in Table I1 show that while .there is fairly close agreement between the results by the two methods when the titrations are made immediately after distillation, in some instances the official method gives loaer results, and when the titration is delayed for several hours the results by the official method are lower in every case. The maximum difference after 9 days amounts to more than 5 per cent of the arsenic present.
Turpentine and Rosin Statistics The production of naval stores this season (1921-22) up t o August 1, according t o reports received from producers by the Bureau of Chemistry, United States Department of Agriculture, was approximately 227,000 casks of gum turpentine and 691,000 round barrels of gum rosin. Estimates on production for the balance of the season indicate a probable total production for the entire season of about 427,000 casks of gum turpentine and 1,320,000 round barrels of gum rosin. Stocks held by producers a t the stills on August 1, 1921, show an increase over similar stocks on April 1, 1921, of about 50 per cent. Stocks held by consumers on August 1, 1921, were practically the same as they were on April 1.
