SULPHATES. 343 



rock-salt of Cheshire yielded in 1000 parts, muriate of soda 983, 

 sulphate of lime 6{-, muriate of magnesia 0^, muriate of lime T \>, 

 insoluble matter 10. Henry. — The principal deposit of salt in this 

 island is that of Cheshire, near Northwich, where there are two 

 beds, of which the uppermost is forty-two yards below the surface 

 and twenty-six yards thick. Rock-salt also occurs at Droitwich, 

 in Worcestershire ; but all the salt manufactured there is said to 

 be procured from springs which rise to the surface. The most 

 celebrated salt mines in Europe are at Cardona in Spain, and in 

 Poland. Rock-salt is also found in vast quantity in various parts 

 of Asia, Africa, and America. The waters of the ocean contain 

 about two and a half per cent, of salt. The uses of this salt in 

 pharmaceutical chemistry are very various and- important. It 

 affords muriatic acid and soda by certain chemical processes. When 

 taken to the extent of half an ounce or more, it acts as a cathartic ; 

 and, dissolved in gruel, it forms the active ingredient in the com- 

 mon domestic enema. Externally, strong brine is sometimes bene- 

 ficially applied to indolent glandular tumours, as a discutient. 



Sp. 2. Muriate of Ammonia, or Sal Ammoniac. This salt 

 is a volcanic production, occuring in fissures, or on the surface of 

 volcanic rocks, and in the vicinity of beds of coal that have been 

 on fire. It is generally of a yellowish or greyish -white colour ; it 

 occurs massive, incrusting and crystalized. The greater part of this 

 salt used in medicine is prepared artificially. As an article of the 

 materia mcdica, it is chiefly limited to external application, as a 

 discutient. 



Genus IV.— SULPHATES. 



Sp. 1. Sulphate of Soda. — This salt occurs in the form of 

 efflorescent incrustations, on rocks and old walls, and dissolved in 

 the waters of lakes. It has long been known under the name of 

 Glauber's Salt, and is prepared by various processes on a large 

 scale. It has a peculiarly bitter nauseous taste, and is less active 

 as a purgative than the sulphate of magnesia. Its medium dose 

 is 3 iss. dissolved in water. 



