278 ANALYSIS OF BRITISH AND FOREIGN SALT. 



Separation and compare the amount of the acid, deducible from the weight 



the C eanh°y n s ^ ° f ^ Sul P hate ° f bar > Tte8 (C ' b *>> with t,,at which ou g ht to 

 phates. exist in the sulphate of lime and sulphate of magnesia, 



actually found by the experiment. But, to make this com- 

 parison, some collateral experiments were previously neces- 

 sary. 



(D. e.) By these experiments I found, that sulphate of 

 lime prepared by double decomposition, then calcined in a 

 low red heat, and afterward dissolved in a large quantity of 

 boiling distilled water, yields, when precipitated by a baFytic 

 salt, in the proportion of 1/5*9 grains of sulphate of barytes 

 from 100 of the calcareous sulphate*. The same quantity 

 of ignited sulphate of lime (~ 12S grains dried at l60 a 

 Fahrenheit,) precipitated by superoxalate of potash, gives 

 102*5 of oxalate of lime ; or, precipitated by subcarbonate 

 of potash at a boiling heat, 74*3 grains of carbonate of limef. 

 One hundred grains of crystallized sulphate of magnesia 

 (zz 56 desiccated) afford, when precipitated by muriate of 

 barytes, 111 or 112 of the barytic sulphate. 



(E.) By a comparison of the above proportions with those 

 obtained in the analyses of any specimen of common salt, 

 we may learn, whether it contain other sulphates beside 

 those with earthy bases. For example, if the precipitate 

 (D.) consist of carbonate of lime only, and bear to the sul- 

 phate of batvtes (C. b.) the proportion of 74 to 175, or very 

 nearly so, we may infer, that no other sulphate is present, 

 but that of lime. The same conclusion will follow, if, after 

 having decomposed one half of the watery solution (G.) by 

 muriate of barytes, and another half by potash, we find 



* This result corresponds, within a fraction of a sprain, with one ob- 

 tained in a somewhat different way by Dr. Marcet ; and very nearly 

 with an experiment of my friend Mr. James Thomson, who found the 

 l>arytic sulphate, precipitated from 100 grains of sulphate of lime by 

 nitrate of barytes, to weigh 173 grains. 



f On reversing this experiment, I found that 100 grains of carbonate 

 of lime, saturated with sulpi.u ic acid, and calcined in a low red heat, 

 afford 135 of sulphate of lime. A similar experiment of Mr. Thom- 

 son gave 134 6 grains. Dr.. Marcet, also, informs me, that from 93-55 

 grains of pure marble he obtained' ] 25 Q5 grains of sulphate of lime, 

 proportions which exactly coincide with those of Mr. Thomson. 



that 



