OF POTASH. 



oxalate of potash, if they should happen to meet 

 with these efflorescing crystals in any of their 

 experiments. 



17. Tartrate of potash. This salt may be ob- Tartralc ' 

 tained in large four-sided prisms, with bases, 

 which are rhombs, with angles of about 93 and 

 87. I have obtained it in veiy large crystals, 

 not less than an inch in diameter. 



To determine the quantity of potash which it 

 contains, I exposed 16\5 grains of it to a heat 

 gradually raised to redness, and kept up the red 

 heat in an open platinum crucible till the tartaric 

 acid was completely destroyed. Water was 

 poured into the crucible, and 9 grains of crys- 

 tals of oxalic acid being added, the crucible was 

 covered with a piece of glass. After the effer- 

 vescence was at an end, the solution was gently 

 evaporated to dryness, and the dry salt redissolv- 

 ed in water. This solution was perfectly neu- 

 tral, for it neither altered the colour of litmus 

 nor cudbear paper ; but 9 grains of crystals of 

 oxalic acid contain just 4\5 grains of true acid, 

 equivalent to an atom. Hence, 16%5 grains of 

 tartrate of potash contain just 6 grains of pot- 

 ash, equivalent to an atom. This potash must 

 be combined with an atom of tartaric acid, equi- 

 valent to 8'5 grains. The remaining 225 

 grains, necessary to make up the weight of tar- 

 trate of potash employed, must be water, and is 



K 1 



