CHROMIUM. 49 



2. Nineteen grains of anhydrous bichromate 

 of potash were dissolved in distilled water, and 

 in another portion of distilled water there was 

 formed a solution of 41 *5 grains of dry nitrate of 

 lead. These two solutions beinff mixed together Analysis of 



11 chromate 



a double decomposition took place ; chromate of and 

 lead was formed, and speedily fell to the bottom 

 of the vessel, leaving a transparent colourless 

 liquid which was not affected by sulphate of 

 soda nor by nitrate of lead, and consequently, 

 contained no sensible quantity either of lead or 

 chromic acid. Thus it appears, that the oxide 

 of lead in 41%5 grains of dry nitrate of lead just 

 saturates the chromic acid in 19 grains of dry 

 bichromate of potash ; but the oxide of lead in 

 41*5 grains of nitrate is 14 x 2 = 28 grains, 

 which is the equivalent for two atoms. Conse- 

 quently, 19 grains of bichromate of potash con- 

 tain a quantity of chromic acid just equivalent 

 to 2 atoms. 



If, instead of 19 grains of bichromate, we take 

 12%5 grains of anhydrous chromate of potash, 

 and 2O75 grains of dry nitrate of lead, the re- 

 sult will be just the same ; namely, the whole 

 chromic acid of the chromate will be precipitated 

 in combination with the whole oxide of lead in 

 the nitrate. Consequently, 12%5 grains of dry 

 chromate of potash contain just the equivalent 

 of one atom of chromic acid. 



The quantity of potash in 19 grains of bichro- 



VOL. II. D 



