182 COAL-TAR COLORS USED IN FOOD PRODUCTS. 



In examining these 30 specimens of the seven permitted colors 

 chemically the following determinations were made: 



1. Moisture. 



2. Chlorin as chlorids. 



3. Sulphated ash, together with its iron, aluminum, calcium, and copper content, 

 and the determination of the sulphuric acid in the sulphated ash. 



4. Total sulphur. 



5. Gutzeit test (test 17 of the United States Pharmacopoeia, eighth revision). 



6. Heavy metals test (test 121 of the United States Pharmacopoeia). 



7. Total insolubles, together with the determination of the proportion that is vola- 

 tile on ignition. 



8. Ether extractive. 



The methods of analysis actually used on these 30 dye specimens 

 are here given solely for the purpose of comparing them with the 

 methods developed therefrom and presented beginning with page 210. 

 Experience has shown that the methods here given are defective in 

 many particulars, and therefore they are not to be used for exact 

 work. 



MOISTURE. 



Dry a sample of each color weighing 3 grams at 105 to 108 C. for two hours. The 

 loss in weight is assumed to be moisture. 



This method is not wholly accurate in the case of Naphthol Yellow, nor is it accu- 

 rate in the case of Amaranth; but the scarcity of material made it seem unwise, at 

 this stage, to undertake any extended investigation as to the amount or nature of the 

 heating required surely to expel all moisture. The results, therefore, while not as 

 accurate as might be desired, are, for the purposes of this exploratory investigation, 

 sufficiently accurate for the object for which they were undertaken. 



CHLORIN AS CHLORIDS. 



Gently heat samples weighing 0.1 gram with 2 grams of sodium carbonate, and after 

 destroying the greater part of the organic matter add 0.1 gram of powdered potassium 

 nitrate and gently heat the whole until the organic matter is entirely destroyed. 

 After cooling treat the whole with small amounts of cold water and remove from the 

 crucible; effect the solution of the whole by gently heating. After cooling bring the 

 bulk to about 150 cc, cool to room temperature, slightly acidify with nitric acid, pre- 

 cipitate the chlorin with silver nitrate, and weigh as silver chlorid. 



SULPHATED ASH. 



Moisten half-gram samples with concentrated sulphuric acid, gently evaporate to 

 dryness, and treat the residue with 5 cc of concentrated sulphuric acid and again 

 evaporate to dryness; repeat the operation until a white ash results, when the whole 

 is ignited to constant weight. After weighing take up the sulphated ash in boiling 

 water (and if necessary, any undissolved material can be taken up with hydrochloric 

 acid by treatment on a boiling- water bath.) Mix the two solutions and bring to a 

 total volume of 200 cc. In one half thereof determine the contained sulphur by a 

 precipitation with barium chlorid, and weigh as barium sulphate; in the other half 

 determine iron and aluminum by precipitation with ammonia, ignite and weigh as 

 ferric and aluminum oxid. No separation of any contained aluminum was under- 



