desirous, for the sake of obtaining further evidence on the subject, to bring the sulphat of alumine to a crystallized state, by artificially supplying what I conceived to be wanting for the completion of that process. For this purpose, having dissolved about thirty grains of residue in distilled water, I added to the filtered solution two or three drops of a solution of carbonat of potash, and evaporated it very slowly; crystals were thus obtained, dispersed in the saline mass, which, though of a size scarcely exceeding that of a pin's head, had a distinct octahedral form, and when separated and chemically examined, had all the properties of alum.
5. With regard to the proportion of sulphat of alumina, contained in the water, it will be seen, that by connecting together the results of the experiments just related (1, 2, 3), eighty grains of residue, or a pint of the water, yield 3,8 grains of alumine heated to redness, which, according to the proportion of twelve parts of ignited alumine, in one hundred parts of crystallized alum[1], would be equivalent to 31,6 grains of alum in each pint of the water[2].
§ X. Sulphat of Lime.
1. Some of the former experiments (§ III. d and g) had shown, beyond all doubt, the presence of selenite, and indeed; from the general composition of the water, lime could scarcely be supposed to exist in it in any other form of combination.
- ↑ These are the proportions stated by Mr. Kirwan, and which I obtained myself on a former occasion (See the Analysis of the Brighton Chalybeate.)
- ↑ It is scarcely necessary again to observe, that the sulphat of alumine contained it the water does not appear to exist there in the state of alum ; but it is perhaps better to express the quantity of alumine by the quantity of alum which it would form, as the crystallised state of a salt affords a much more precise standard of comparison.
