434 Researches upon the Heat developed 



becomes gray like charcoal powder : in this way it assumed 

 a blueish shade. 



Experiment 20. — Deutox'ide of Copper. 

 lis colour is a deep gray containing a little brownish red. 

 On exposing it to heat, it becomes blacker, which proves 

 that it has taken from the blue which has neutralized the 

 red and the yellow. 



Experiment 21. — Dentoxide of Iron. 

 It is of a gray colour, retaining very little of the brownish 

 red. Heat produces blue, and its colour becomes of a purer 

 gray, which by opposition makes the former appear redder. 



Experiment 2Q. — Peroxide of J ntiviony ; Pearl Powder 

 of Kerkrivgius. 



Its colour is a bright white, like white lead. When heated 

 it takes a slight shade of dirty yellow or yellowish gray. 

 We obtain a similar effect with the volatile oxide of anti- 

 mony, but in a feebler degree. 



LXVI. Researches upon the Heat developed in Comlittstion, 

 and in the Condensation of Fuponrs. Read before the French 

 Institute on the lAlh of February and 30th of November 

 1812. By Count Rum ford, F.R.S. Foreign Associate 

 of the Imperial Institute of France, &c. ^c. 



[Continued from pafje297] 



§ V. Heat developed in the Combustion of Spirit of Wine 

 and Alcohol. 



As the constituent parts of these inflammable liquids may 

 be regarded iii well determined, bv the results of M. de 

 Saussure's excellent work, I undertook a second time to 

 examine them, with a view to what were the quantities ot the 

 heat which are developed during their combustion. I had 

 begun this business five vears ago; but after having made 

 a considerable number (if experiments, I abandoned it on 

 account of the great diffii ultics which I met with; but the 

 instant I found means to make my apparatus more perfect 

 I recommenced. 



Before giving the details of my experiments, I ought to 

 say a few words upon the difficidties which attended the 

 enterprise, even since I possessed my new apparatus, and 

 upon the means 1 used to surmount them. Ihere were 

 even dangers to which I was exposed, which it is necessary 



I should 



