The following has been recommended as an eligible mode of fumigating rooms for the prevention of infectious disorders. Take six drachms of powdered nitre ([206]), and six drachms of sulphuric acid (spirit of vitriol); and mix them in a tea-cup, by adding to the nitre one drachm at a time of the oil. During the preparation the cup must be placed on a piece of heated iron, and the mixture stirred with a tobacco pipe or piece of glass. As soon as the fumes arise, the cup must be moved about to different parts of the room or house that are to be fumigated.
203. GLAUBER SALT, or SULPHAT of SODA, is a salt which consists of soda ([200]) in combination with sulphuric acid ([24]). It occurs in an efflorescent or powdery state, on the borders of salt lakes; or, more commonly, in a state of solution, in certain mineral waters.
This salt, which was originally discovered by a German chemist whose name was Glauber, has a nauseously bitter and saline taste. It is found, in an efflorescent state, on meadow ground at Eger, in Bohemia; and on the walls of old galleries in mines, at Grenoble, in France. It is also abundant in the ashes of some kinds of vegetables, especially of sea weeds. The waters of the Mediterranean yield a great proportion of it; and the Glauber salt used for commercial purposes is chiefly prepared from sea-water, or by decomposing common salt, in order to procure muriatic acid ([29]). It may also be obtained by saturating soda with sulphuric acid ([24]).
The use of this salt in medicine is well known; and, in some countries, it is employed as a substitute for soda ([200]), in the manufacture of white glass. It ought to be kept in well-corked bottles, as otherwise the crystals soon fall into powder.
The following is a pleasing experiment, which shows a singular and almost instantaneous crystallization of Glauber’s salt. Dissolve this salt by adding portions of it gradually to water kept boiling until the water will dissolve no more. Pour the solution, whilst boiling, into common medicine phials previously warmed, and immediately cork them. Set the phials in a quiet place without shaking them. The solution, when cool, will remain perfectly fluid till the cork is taken out; but the moment this is done, and the air is admitted, it will begin to crystallize on its upper surface, in fine satin-like crystals, which will shoot downward, like a dense white cloud. In this act so much heat becomes evolved as to make the phial feel sensibly warm to the hand. When the crystallization is complete, the whole mass generally becomes so solid, that, on inverting the bottle, not a drop of it will fall out. If the crystallization should not immediately ensue on opening the phial, this may instantly be effected by dropping into it a minute crystal of the same salt. The experiment may be exhibited any number of times afterwards, by merely placing the phial in boiling water, till the salt it contains be again completely liquefied; and letting it stand, as before, to cool.
204. BORAX is a salt composed of boracic acid ([28]) and soda ([200]), and is imported chiefly from the East Indies, in the form of a brownish grey, impure, shapeless salt, of sweetish taste; or in detached prismatic crystals, each about an inch in length.
Although borax has long been known as an article of traffic, there is scarcely any production with the origin of which we have been, till lately, less acquainted. It is found in a native, though impure state, in a mountain lake, situated about fifteen days’ journey from the capital of Thibet in the East Indies. This lake is so encompassed with hills as to have no stream either falling into it or flowing from it. The water is salt to the taste, and contains both borax and common salt; and the edges and shallow parts are covered with a stratum of this substance, which is dug up in considerable masses for exportation. It has here the name of tinkal, and is usually brought into Europe enveloped in a kind of fatty substance. The mode of refining it was for a long time kept, by the Dutch and Venetians, amongst those secrets which a want of sufficient research alone prevented from being generally known. When refined, it is called borax.
The uses of borax are numerous. It is employed as a flux for metals, being found to produce a more perfectly limpid fusion than any other substance. For the same reason it is made an ingredient in the finest kinds of glass, and particularly in some of the coloured glass pastes which are manufactured in imitation of gems. But its chief use is to jewellers and goldsmiths, to facilitate the soldering of gold and silver. Borax is also used in medicine.
205. POTASH FAMILY.
Potash is an alkaline substance ([42]), of white colour, and of smell somewhat resembling that which is perceived during the slaking of quick-lime ([137]). It is extremely corrosive, and remarkably acrid to the taste.