COMPILATION OF LAWS. 51 



Remark: If a color is so scant (for example, on toys, lamp stands, candies, etc.) 

 that you can not find 1 gram, perform the experiment with the material on hand 

 and judge the result in accordance with the following directions in the same way 

 as though the amount prescribed had been used. 



The experiment is to be performed according to the methods described below, 

 and the following apparatus and tests are to be used: 



1. A Marsh -Berzelius apparatus, consisting of a gas-generating flask of 200 cc, 

 with a calciuni-chlorid tube and heating tube of heavy fusible glass, which at 

 the point of expansion where the arsenic, if any, would gather, has a diameter of 

 1.5 to 2 mm. 



2. Flat-b3ttomed retort (Erlemneyer's) of about 250 cc. 



3. Porcelain crucible of 50 to 60 cc. 



4. Hydrochloric acid without arsenic (about 15 per cent). 



5. Ditto zinc. 



6. Ditto potassium chlorate. 



7. Ditto anhydrous sodium chlorate. 



8. Alkaline solution of sodium hypochlorite containing about 2 per cent of 

 this salt. 



The purity of the reagent is tried in the Marsh apparatus by using a blank of 

 100 cc of hydrochloric acid, 25 grams of zinc, 5 grams of potassium chlorate, 5 

 grains of sodium chlorate, and 5 cc of the sodium hypochlorite. 



When these quantities of the reagents in the Marsh apparatus do not produce a 

 dark coating in the tube after being heated 35 minutes, accompanied by a produc- 

 tion of gas which produces at the end of the tube a flame 4 to 8 mm long, it is to 

 be considered free from arsenic. 



As a measure in case of experiments for arsenic, an arsenic mirror is used, 

 which is prepared by means of an arsenic solution containing 0.1 of mg arsenic in 1 

 cc. The measuring mirrors are produced by adding to the Marsh apparatus, after 

 it is started and -the tube has been heated not less than five minutes, 1 cc of arsenic 

 solution, and thereupon heating the tube twenty minutes with a gas generation of 

 the power mentioned above. The tubes in which these arsenic mirrors are pro- 

 duced, each of which thus corresponds to 0.1 mg arsenic, are fused while yet 

 connected with the gas-generating flask in such a way that they become filled 

 with hydrogen gas. 



In order to obtain a solution suitable for a test in the Marsh apparatus, one 

 treats the different objects in the following way: 



A. Cloths and yarn, artificial flowers, dry colors, and water colors that have 

 been scraped off are treated, in the quantity mentioned above, in a flat-bottomed 

 retort with 30 to 60 cc of muriatic acid and 0.5 to 2 grams of potassium chlorate. 

 The retort is heated while constantly shaken till its contents approach the boiling 

 point. When the colors are destroyed as far as possible, the solution is poured 

 from the insoluble residue into another retort and is boiled till there is no smell 

 of chlorin. 



B. As for articles of paper, oil-coated cloths, and oil colors scraped off, it is 

 necessary to burn the organic matter. In order to do this, one heats in one of the 

 porcelain crucibles mentioned among the apparatus 6 to 10 grams of a mixture of 

 two parts potassium chlorate and one part sodium chlorate. When the heating 

 has gone so far that a bit of the article pressed down into the crucible with a 

 glass stick begins to burn immediately, one removes the lamp and adds little by 

 little parts of the sample which have been cut into not less than ten bits, stirring 

 now and then the contents of the crucible with a glass stick, taking care that there 

 is always on hand a surplus of oxidizing material. The contents of the crucible are 

 now dissolved in muriatic acid and the solution boiled till it ceases to smell of 

 chlorin. 



