OF COBALT. 317 



1 atom oxalic acid 4-5 



1 atom protoxide of cobalt 4'25 



2 atoms water 2-25 



11 



10. Tartrate of cobalt. This salt was obtained Tartratt> 

 by dissolving oxide of cobalt (from an ammonia- 

 cal solution) in tartaric acid. By digesting the 

 acid over the oxide for twenty-four hours, a fine 

 crimson solution was obtained, which, when con- 

 centrated by evaporation, let fall a red precipi- 

 tate having a most beautiful crimson colour. 

 This precipitate was put on a filter and washed 

 with water two or three times to remove any 

 excess of acid that might adhere to it ; it was 

 slightly soluble in water, for by this process its 

 quantity was sensibly diminished, while the wa- 

 ter with which it was washed came off red. The 

 matter was now dried on the filter in a gentle 

 heat ; it had a fine crimson colour, little or no 

 taste, but it reddened vegetable blues. 7*8 

 grains of this salt, being exposed to the highest 

 temperature they could bear without decompo- 

 sition, lost 1 *5 grains of their weight : leaving 

 6-55 grains of tartrate still retaining its fine co- 

 lour. Now, 



6-55 : 12-5 :: 1-25 : 2-3? 1 = water combined with an 

 integrant particle of anhydrous salt. 



This shows us that the constituents of the salt 

 are 



