642 Metallic Preparations. — Antimony. part in.
By all these methods, a little modified, crystallized tartar eme-tic may be prepared. With regard to the formula of the Lon-don college, the instructions for conducting the process aresuch as are likely to mislead any one not much accustomed tothink on chemical phenomena. Thus it is not perfectly ap-parent whether the fluid which passes the filter, or the residuewhich remains on it, is to be boiled to dryness. The directionas I have stated in another quarter ' should be " turn cola, etreliquum super chartam bibulam calore exsicca," &c. Afterrepeated trials we have found the following circumstances ne-cessary to be attended to, to insure success. In the first placethe sulphuret of antimony must be very finely pulverized in aniron mortar, then well mixed with the nitrate of potass, alsoreduced to a fine powder, and the mixed powders added bydegrees to the mixture of the acid, with the whole of the waterheated to 180°, and kept in this temperature for some timeafter all the powder has been added ; the supernatant fluid 13then to be decanted off, and the residuum washed with distilledwater until the fluid comes off tasteless. We have found noadvantage from drying the residuum ; but while it is yet moist•with the last washing, the supertartrate of potass should beadded ; and after stirring them well together, the whole throwninto a pint of distilled water. The mixture is then to be boiledfor half an hour, filtered whilst it is hot, and the fluid setaside in a flat vessel to crystallize. When the solution hasbeen boiled too long, the crystallization is very irregular.
The following is the probable theory of the changes whichtake place during the process we have described:—The nitrateof potass is decomposed by the sulphuric acid, as is demon-strated by the extrication of nitrous gas; and part of its oxy-gen is expended upon the oxide of the sulphuret. This isconverted into protoxide of antimony; while, perhaps also atthe same time, the sulphur is partly converted into an acid.Sub-sulphate of antimony is then formed by the action of partof the acid on the protoxide, which has a greyish appearancewhen washed, and is in a state fit to be acted upon by thetartaric acid of the supertartrate of potass, and form the ter-nary salt.
T The theory of the other two processes is sufficiently obvious.The superabundant acid of the supertartrate of potass combineswith the oxide of antimony, forming a triple salt, or a tartrateof antimony, and of potass; which, on the principles of the re-formed nomenclature, should be the pharmaceutical name ofthis salt.
It must be regretted that all the colleges have not concur-
1 Land. Med. Repository, vol. iv. p. 131.