One thousand experiments in chemistry : with illustrations of natural phenomena ; and practical observations on the manufacturing and chemical processes at present pursued in the successful cultivation of the useful arts / by Colin Mackenzie.

Date:
1821
Catalogue details

Licence: Public Domain Mark

Credit: One thousand experiments in chemistry : with illustrations of natural phenomena ; and practical observations on the manufacturing and chemical processes at present pursued in the successful cultivation of the useful arts / by Colin Mackenzie. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    from the impurities which remain, but it must not be filtered, as that operation would deprive the Lac of some of its qua- lities. Observation. In cases where a greater degree of hardness in the var- nish is desirable, and its colour is but a secondary consideration, one part of shell lac with eight parts of alcohol, is to be preferred. dccccxcvit. Copal Varnish. Reduce to powder an ounce of pure Carbonate of Potass, and then lay it before the fire, till it becomes hot and dry. In this state, put it into a pint of Alcohol, or Oil of Tur- pentine. All the watery particles contained in the Oil or Spirits, will be absorbed by the Alkali; and the Alcohol, or Turpentine, will thus become pure, or highly rectilied. This process is called Alkalizing these solvents. Now put the Turpentine or Spirits into a vessel with two ounces of clear dry Copal, finely pounded and sifted : place the vessel in warm Water; the Copal will be soon dissolved. Observations. This varnish, which is principally applied to wood, paste-board, and prints, is to be diluted by a little warm oil of turpen- tine, before it is used. If the spirits of turpentine be alkalized when the copal is dissolving, a little spirits of wine should be added; and if the spirits of wine be alkalized when the copal is dissolving, a little spirits of turpentine should be added: the sediment of the varnish will dry on the silk in a few hours ; the thicker the varnish, the sooner it dries. Dccccxcvnr. Varnish for Oil Paintings. Mix six ounces of pure Mastich Gum with the same quantity of pounded Glass, and introduce the compound into a bottle containing a pint of Oil of Turpentine ; (treat- ed with Alkali as above), now add half an ounce of Cam- phor bruised in a mortar. When the Mastich is dissolved, put in an ounce of Venice Turpentine, and agitate the whole till the Turpentine be perfectly dissolved. Observations. When to be used, this varnish must be gently poured off the glass sediment at the bottom of the bottle ; or it may be filtered through muslin. The intention of using ground glass, is to present a greater surface of mastich, to the solvent, by throwing the particles as much apart as possible. nccccxcix. Lacquer, or Varnish for Tin Ware. Put three ounces of Seed Lac, two drams of the sub-