British and Foreign Salt. 173 



hi ho instance found uncombined ; but in the majority of 

 cases (as in the earthy muriates obtained from Cheshire) 

 salt was mixed with muriate of magnesia. 



(B.b.) TV the solution of two earthy muriates was 

 added fully'saturaied carbonate of ammonia, which has thd 

 property of throwing down lime in combination with car- 

 bonic acid, but has no effect on the muriate of magnesia at 

 ordinary temperatures. The 'solution of the latter salt, along 

 with that of the excess of carbonate of ammonia, was 

 therefore separated by filtration ; and to the filtered liquor a 

 solution of phosphate of soda was addedj according to the 

 formula of Dr. Wollaston*. 



(B.c.) By direct experiments I had learned that 10O 

 grains of muriate of magnesia, when thus decomposed by 

 carbonate of ammonia, conjoined with phosphate of soda, 

 give 151 grains of an insoluble ammoniaco-magnesian 

 phosphate dried at about 90° of Fahrenheit. Hence it wag 

 easy, from the weight of the precipitate, to calculate how 

 much of the former salt was contained in the mixture 

 of muriate of lime and muriate of magnesia. Thus, if 20 

 grains of a mixture of the two muriates yielded l.W of 

 ammoniaco-magnesian phosphate, it is obvious that the 

 mixture must have consisted of equal weights of muriate 

 of lime and muriate of magnesia. 



(B. d.) T«he estimation of the proportion of muriate of 

 rime, in a mixture of this salt with muriate of magnesia, 

 vvas sometimes performed in a diti'e rent way. To a cold 

 solution of a known weight of the two salts, super-oxalate 

 of potash was added ; and the precipitate was collected, 

 washed, and dried at about {CO' 5 Fahrenheit. Of this pre- 

 cipitate f had previously found that 1 16 grains are formed 

 by the decomposition of 100 grains of dry muriate of lime. 

 From the qiiantit/of oxalate of lime it was easy, therefore, 

 to infer that of the muriate, from whose decomposition it 

 resulted ; and this subtracted from the weight of the two 

 salts^ gave the weight of the muriate of magnesia. 



II. To separate a fid estimate the earthy Sulphates. 



(C.) The portion of salt which had resisted the action 

 of alcohol, was dissolved by long boiling in sixteen ounce 

 measures of distilled water, and the solution was filtered. 

 On the filter a small quantity of undissolved matter ge- 

 nerally remained, which was washed with hot water, till it 



• * See Dr. Marcet's analysis of the Brighton Chalybeate, published in th$ 

 last edition of Saunders, on Mineral. Waters. 



ceased 



