208 ESSAY XVIII. 



till there appeared no more effervescence. A coagulation 

 immediately took place, in consequence of the formation of 

 small crystals, which required eight times the quantity of 

 boiling water for their solution. After it was cold the 

 greatest part of the crystals separated again from it. With 

 mineral alkali this acid showed the same phenomena, with 

 this difference, that the neutral salt thus arising requires 

 only five parts of boiling water for its solution. If to a 

 solution of it a solution of alkali of tartar be added, a 

 number of small crystals will be soon formed at the bottom 

 of the vessel, on account of the greater affinity of this acid 

 with the latter alkali. Both these salts are perfectly neutral. 

 Saturated with volatile alkali it forms a kind of sal 

 ammoniac, which, after being gently dried, has a sourish 

 taste. When distilled, the volatile alkali is first separated, 

 the lime-water precipitates ; the acid remaining in the retort 

 afterwards yields, with a stronger heat, the same products as 

 in Sec. vi. 



SECTION VIII. WITH EARTHS. 



The acid of the sugar of milk forms, with all the earths, 

 salts insoluble in water. I shall therefore only relate the 

 experiments which I made with it in the way of precipitation. 

 If a solution of the ponderous earth in muriatic or nitrous 

 acid be dropped into a cold solution of our acid (Sec. vi.), the 

 earth is immediately precipitated in combination with this 

 acid. With the same solutions of lime this acid exhibits 

 the same phenomena ; but the solution of gypsum remains 

 undecomposed. The same thing happens with the solutions 

 of magnesia in vegetable or mineral acids, and with earth of 

 alum ; all of which, however, are decomposed by the neutral 

 salts above mentioned. 



