248 SALTS 



be concentrated) under the exhausted receiver 

 of an air pump, standing over a vessel filled with 

 concentrated sulphuric acid. The water and 

 excess of ammonia gradually evaporate, and 

 leave the chromate of ammonia behind in a dry 

 state. It has a fine yellow colour, and is in crys- 

 talline scales, which are not altered by exposure 

 to the air. Its taste is hot and saline, and it is 

 exceedingly soluble in water; it produces no 

 alteration on cudbear paper, but very slightly 

 reddens litmus paper. Solutions of 8*625 grains 

 of this salt and 2O75 grains of nitrate of lead 

 being mixed together, chromate of lead precipi- 

 tated, and the supernatant liquid was transpa- 

 rent and colourless, and contained no traces of 

 chromic acid or of lead. Hence, the salt is an- 

 hydrous and composed of 



1 atom chromic acid 6-5 

 1 atom ammonia 2-125 



8-625 



12. Bichromate of ammonia. This salt is ob- 

 tained when we concentrate the solution of 

 chromate of ammonia on the sand bath. One 

 half of the ammonia flies off, and the bichromate 

 gradually precipitates in the form of beautiful 

 red crystalline scales, which are not altered by 

 exposure to the air. The taste of this salt is 

 hot, and bitter, and very disagreeable ; it reddens 



