ANALYSIS OF PERMITTED COLORS, 1907. 183 



taken in the nitrate from the iron; the lime was precipitated as oxalate. In the only 

 case that copper was encountered it was precipitated as sulphid before taking out the 

 iron or the calcium. 



TOTAL SULPHUR. 



Mix 0.2 gram of the sample with 4 grams of sodium carbonate and 0.5 gram of potassium 

 nitrate, and ignite to complete the destruction of the organic matter; take up in hot 

 water; acidify with hydrochloric acid and precipitate the sulphur as barium sulphate 

 with barium chlorid. 



GUTZEIT TEST. 



Mix 2 grams of the substance with 2 grams of a mixture of 1 part of potassium nitrate 

 and 5 parts of sodium carbonate and ash in a porcelain crucible over a low flame; if 

 not white when cool, mix the ash with 1 gram of potassium nitrate and again ash over 

 a low flame. Generally the second ashing is sufficient. Dissolve the residue in 50 

 cc of hot water, boil, filter, neutralize with dilute sulphuric acid, and evaporate to 

 substantial dryness on a boiling- water bath. Then add 1 cc of concentrated sulphuric 

 acid and dry over a Bunsen flame; take up the residue with 5 cc of distilled water 

 containing 0.5 cc of concentrated sulphuric acid and 10 cc of a saturated solution of 

 sulphurous acid; evaporate the whole to a bulk of 5 cc on a water bath; add 20 cc of 

 8 per cent hydrochloric acid and subject this material to the action of 2 grams of metallic 

 zinc, free from arsenic, which has been so activized by means of platinic chlorid that 

 at the end of two hours more than 1 gram of zinc has dissolved and the evolution of 

 gas has been constant and continuous. Conduct the reaction in a flask of 60 cc capacity 

 with a neck 1 cm in diameter and 6 cm long. After the introduction of the solution and 

 the zinc into the flask, stopper the neck of the bottle with gauze, the lower half of 

 which is dry and the upper half moistened with the test solution of lead acetate of 

 the United States Pharmacopoeia. After carefully wiping the lip of the flask, cover 

 it with Schleicher & Schiill quantitative filter paper which has been saturated three 

 times with alcoholic mercuric chlorid solution, with complete drying between each 

 saturation on one and the same spot of the filter paper. 



In the case of Naphthol Yellow S it is necessary to heat gently with 10 grams of 

 sodium carbonate until the organic matter is substantially all destroyed, then add 

 1.5 grams of potassium nitrate and heat to complete destruction of the organic matter. 

 Dissolve the fused mass in hot water and a few drops of fifth-normal sulphuric acid; 

 then make distinctly acid with the same and add an excess of 1 cc of concentrated 

 sulphuric acid; evaporate first on the water bath and afterwards on asbestos until all 

 odor of nitrous fumes and of hydrochloric acid has disappeared. Take up the residue 

 in 5 cc of water and 15 cc of a saturated solution of sulphurous acid in water. Heat 

 the whole on the water bath until no odor of sulphur dioxid remains. 



The preparation of the sample by ignition with carbonate and nitrate should not 

 be done in platinum, but should be done in a porcelain crucible, since it has happened 

 that as much as 0.05 mg of arsenic mixed with the dye, which had been fused in 

 platinum with carbonate and nitrate, could not be detected on the mercury-chlorid 

 paper, whereas 0.01 mg when similarly treated in porcelain could always be detected, 

 and 0.005 mg would usually be found when done in porcelain. 



HEAVY METALS. 



Mix as much of the substance as approximately contains 1 gram of color with 10 

 times its weight of carbonate of soda and ignite with the addition of 0.5 gram of potas- 

 sium nitrate. Dissolve the whole in water, any undissolved material being taken up 



