Chemistry, lix 
tion of sulphate of lime till all the sulphate of magnesia be 
dissolved. The sulphate of lime remaining is dried and weighed, 
Its weight subtracted from that of the original weight of the 
sulphates gives the sulphate of magnesia. ‘The only part of this 
formula that requires verification, 1s that part of it in which it 
is supposed that when water saturated with sulphate of lime is 
digested in a mixture of sulphate of magnesia and sulphate of 
lime, it is incapable of dissolving any additional portion of 
sulphate of lime. Many salts have the property of increasing 
the solubility of others in water. It would be necessary, there- 
fore, before giving full credit to Mr. Philips’ ingenious modifica- 
tion of my formula, to ascertain that sulphate of magnesia does 
not possess the property of increasing the solubility of sulphate 
of lime in water. —(Institution Journal, vi. 313.) 
2. Separation of Iron from Manganese.—This :is another 
analytical process, scarcely less difficult than the preceding. 
Many methods have been given, most of which I have tried 
without being fully satisfied with any of them. Gehlen’s method 
of throwing down iron when in the state of peroxide, by means 
of succinate of ammonia, answers very well ; but it is too expen- 
sive for common use, especially when the quantity of iron is 
considerable. Hisinger’s substitution of benzoate of ammonia 
or of potash, is probably a great improvement ; but I have not 
examined this method with sufficient care to enable me to form 
an opinion. Mr. Hatchett’s method of throwing down the iron 
‘from manganese by ammonia, when both are held in solution by 
muriatic acid, answers very well for procuring manganese free 
from iron; but it is not so easy by means of it to determine 
exactly the proportions of manganese and iron in the solution ; 
and in cases of complicated mineralogical analyses, this method 
cannot. be put in practice at all. 
Mr. Faraday has suggested two methods of separating these 
two metals from each other; neither of which I have yet tried ; 
but they promise to furnish us with more’precise analytical re- 
sults than any which have been yet proposed. The first of his 
methods is this : 
“ To a mixed solution of iron and manganese, add solution 
of sulphate or muriate of ammonia; then pour in pure potash ; 
the iron will be precipitated, but the manganese will remain in 
solution in the state of a triple salt.” 
Another method suggested by him is this : 
Let the iron in solution be brought to the state of a peroxide ; 
throw down the oxides of iron and manganese together, wash 
them by decantation, and digest them in a solution of sal-am- 
moniac with a little sugar; the manganese will be dissolved in 
what state soever of oxidation it is, but the iron will remain,— 
(Institution Journal, vi. 357.) 
It seems unnecessary to allude to Grotthuss’ method of sepa- 
rating these two metals by means of sulpho-chyazic acid (Annals 
