238 Dr. Marcet on an Aluminous Chalybeate Spring 



the basis, and also to assist me, as will be seen hereafter, in forming 

 certain inferences with regard to the alkaline salts. For this pur- 

 pose I made the following experiments. 



1. To four ounces of the water was added nitrat of barytes till 

 the whole of the sulphuric acid was precipitated ; the sulphat of 

 barytes thus obtained being carefully edulcorated and heated to red- 

 ness in a platina crucible, weighed 1S,5 grains, which correspond to 

 *74 grains of sulphat of barytes from a pint of the water. 



2. Four ounces of the water were treated with nitrat of silver as 

 long as any precipitate appeared, and the muriat of silver thus 

 obtained, being well edulcorated, and afterwards brought to a state 

 of incipient fusion by the heat of an Argand lamp, weighed 2,05, 

 which is equivalent to 8,2 grains of luna cornea, or four grains of 

 muriat of soda,* in each pint of the water.f 



§ XIV. Sulphat and Muriat of Soda. 



1. The mode in which I first attempted to ascertain the presence 

 of alkaline salts in the water, was that alluded to in a former part of 

 this paper, which consisted in precipitating the iron and the earths 

 by subcarbonat of ammonia, evaporating the clear solution to dryness, 

 heating the dry mass to redness, with a view to drive off the sulphats 

 and muriats of ammonia, redissolving the residue in water, and eva- 



* I have found by direct experiments that one hundred grains of pure muriat of soda 

 heated to redness, and decomposed by nitrat of silver, yield 241,6 grains of luna cornea 

 heated to fusion^ 



+ The same experiment was tried three times upon different specimens of the water, 

 and I here give the average. The smallest quantity of luna cornea obtained was two 

 grains, and the largest 2,5 grains, a difference too great to arise from mere inaccuracy. 

 From this and several other circumstances I have reason to suspect that the water is sub- 

 ject to occasional variations in the proportions, as well as in the aggregate quantity of its 

 solid contents. 



