2384 AN ANALYSIS 
The difficulties attending the perfect separation of com- 
pound salts from each other, by crystallization, even with the 
aid 
edges, considering the rhomb as a four-sided prism, and transparent. The cry- 
stals are permanent in the air; they are soluble in little more than three times 
their weight of water, at the temperature of 60°; they do not undergo the 
watery fusion from heat, but suffer decrepitation. In. these properties, this salt 
differs entirely from sulphate of soda, or sulphate of magnesia. 
To determine its composition, 20 grains reduced to powder were exposed 
to heat, raised gradually nearly to redness ; they lost from the escape of water 
5.6 grains. The residual powder was dissolved in water, and muriate of ba- 
rytes was added as long as any precipitation was produced. The precipitate 
dried at a red heat, weighed 23.9 grains, equivalent to sulphuric acid 8.2 
grains. To the clear liquor carbonate of ammonia was added, which did not 
impair the transparency ; phosphoric acid was then dropped in, which produ- 
ced a copious precipitation. The precipitate, calcined at a red-heat, weighed 
5.3 grains, equivalent to 2.1 of magnesia, or 6.4 of sulphate of magnesia ; 
the residual liquor being evaporated to dryness, the dry mass was submitted 
to heat, gradually raised, as long as any vapours exhaled ; it afforded, by solu- 
tion in water and evaporation, muriate of soda in cubes, which, after expo- 
sure to a red heat, weighed 6.4 grains, equivalent to 7.8 grains of sulphate of 
soda. 100 grains of the salt, therefore, afford of 
Sulphate of Magnesia, — 32 grains. 
Soda, - 39 
Water of Crystallization, - 28 
Loss, - - 1 
100 
It afforded also a slight trace of muriatic acid; its solution being in a very 
slight degree rendered turbid by nitrate of silver, probably owing to the inter- 
mixture of a little muriate of soda, as an extraneous ingredient, ‘This ac- 
counts for the proportion of sulphuric acid, as inferred from the quantities of 
the bases, being a little larger than that directly obtained by the precipitation by 
muriate of barytes. 
The difference of crystalline form, as well as other differences of proper- 
ties in the salt from those, either of sulphate of soda or sulphate of magnesia, 
sufficiently prove that it is not merely an intermixture of the two, but that it 
is of definite composition. It deserves to be remarked, too, that it has not 
the same relation to water that either of these salts has, or any mean be- 
tween 
