♦ 



Miscellanies. 201 



In performing this process, care must be taken to heat the mixture 

 gradually, and not to raise the temperature above 80° of Reaumur 

 (=212° Fahr.) This heat is sufficient to effect the coction of the 

 flour and of the muco-extractive portion of the oil, — a stronger heat 

 would color the oil, and thus injure the sale of it. 



I was led to this process, observes Curaudau, by an observation 

 which every body may have made ; viz. that a clear white sauce, 

 when overdone, separates into two parts ; the one thick, occupying 

 the bottom of die vessel, the other clear, and swimming on the de- 

 posit ; the first substance is the caseous part of the butter united to 

 the flour, which is added to the sauce and which the coction has sepa- 

 rated from the oil ; the second is the butter deprived of all foreign 

 ingredients. In this state it may be called depurated or clarified 

 butter. These remark are altogether applicable to oil and fat. 



To this simple observation I owe the idea of purifying oils by flour 

 and water, which affords great advantages. 



Lamp oil needs purification to render it fit for combustion. This 

 is no other than depriving it of a muco-extractive substance, which 

 united to the heterogeneous matters that are mingled with it, hinders 

 it from giving, during combustion, a pure light. Since the introduc- 

 tion of the argand lamp, more attention has been given to the purifi- 

 cation of oil. 



Another method. — The process of M. Thenard, somewhat mod- 

 ified, is to add one part of sulphuric acid of commerce, diluted with 

 ten times its weight of water, to one hundred parts of oil of Colza : 

 agitate well the mixture as soon as the materials are well incorpora- 

 ted, let it rest until the oil becomes clear. An acid liquid collects at 



* 



the bottom, a little colored. The acid is separated from it, and to 

 ensure its freedom from acid, a few ounces of pulverized chalk, or 

 white marble, are well shaken up with it, and it is again left to become 

 clear by repose, and then decanted. 



The effect of the acid, although so much diluted, is to deprive the 

 oil of all its moisture, and of its muco-extractive portion, which 

 diminishes the energy of the combustion, carbonizes the wick, and 

 occasions smoke. — Jour de Con. UsueL torn. 13, p. 21. 



NATURAL HISTORY. 



1. 



Thermal spring in the bed of the Rhone. — M. De Carpen- 

 tier, director of the salt works at Bex, in Switzerland, describes a 

 new thermal spring in the bed of the river, about ten thousand feet 



Vol. XXIV.— No. 1 . 26 



