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XXVIII .^Description of a Furnace destined for the IJquc* 

 faction of Copal and Amhcr. By Professor Tingry*. 



JL hose who have examined in detail the laboratories de- 

 Mined for a course of chemistry, may easily form a clear 

 idea of the construction of this furnace, by recollecting that 

 employed for separating sulphuret of antimony from its 

 matrix. Bui to render it fit for the object in question re- 

 quires some alterations ; by the help of which one may use , 

 it without inconvenience for the liquefaction of solid resins, 

 and even for mixing them with drying oils. 



This furnace, a section of which is represented fig. 1. 

 Plate II, may be entirely constructed of burnt clay, three 

 large apertures being made in the lower chamber, A, which 

 supplies the place of an ash-hole in the common furnaces. 

 The upper part of these apertures is arched ; and the pillars 

 or solid parts between them should be as narrow as possible, 

 in order to enable the artist with facility to extract the li- 

 quefied matter, and even to mix it with the drying oil, if 

 this Kind of varnish be required. 



The upper part, B, or fire-place of the furnace, is sepa- 

 rated from the lower part, A, by a bottom or plate, which 

 answers the same purpose as a grate in the common furnaces. 

 This plate has in the middle a circular aperture, the diame- 

 ter of which corresponds to that of the tube, C, which it 

 is destined to receive, and which extends a considerable way 

 below it. This plate may either form one piece with the 

 furnace or may be moveable. In the latter case it is sup- 

 ported by three projections, or by a circular ledge which 

 projects inwards. In my furnace this partition is composed 

 of an iron plate covered with a coating of potters' clay an 

 inch in thickness. This precaution is indispensably neces- 

 sary, to prevent the heat from penetrating to the lower di- 

 vision, A. 



The sides of the fire-place, B, are pierced with holes an 

 inch in diameter, and distant from each other about three 

 inches. These apertures admit air sufficient to maintain 

 the caloric (heat) at the degree proper for this kind of ope- 

 ration. The following are the proportions of the three parts 

 of this furnace, which served me for my experiments, and 

 in which I liquefied six ounces of copal in the space of ten 

 minutes, without altering its colour in a sensible manner. 



* From his work entitled «* The Painter and Pamuheri Guide" Eng- 

 lish edition. 



M 4 Total 



