|22 ON THE HEAT DEVELOPED IN COMBUSTION. 



Without this precaution ; in experiments made with ether, 

 so large a quantity of this volatile liquid would evaporate 

 through the nozzle of the lamp while weighing, that it would 

 be impossible to ascertain the quantity burned. 



The nozzle of the lamp is steadied by two pieces of wire, 

 proceeding from it horizontally, and soldered to the body of 

 the lamp. 



To keep this lamp constantly cold, as well as the liquid it 

 contains, it is placed in a small pan, and covered completely, 

 except the extremity of its nozzle and that of its neck, with 

 a mixture of pounded ice and water. 

 Caution. When the lamp is weighed, it is taken out of the pan, and 



well wiped with a dry cloth, before it is put into the scale. 



When the lamp is kindled, the operator must not forget, 

 after it has burned two or three minutes, to open the screw 

 that closes its stopple a little, though but very little^ other- 

 wise it might go out. 



As the little horizontal tube, by which the liquid that is 

 burned passes from the reservoir of the lamp to its nozzle, is 

 always filled with liquid, so that it can have no communica- 

 tion with the vapour diffused in the upper part of the reser- 

 voir, this vapour cannot escape by the nozzle of the lamp, as 

 it did before I thought of this method of preventing it. 

 a i « If I have been very minute in my description of this lamp, 



minuteness, it. was because I thought it necessary to spare those, who 

 might be disposed to repeat my experiments or make similar 

 ones, all the difficulties I had to surmount, before I found the 

 means of having under command the combustion of very 

 volatile inflammable liquids. 



As the apparatus [ have employed has now been described, 

 it will be easy to follow the steps of ray experiments, and to 

 appreciate their results. I will endeavour to describe them 

 clearly, but also as briefly as possible. 



.... , Having procured a stock of spirit of wine of the shops, and 



^p^^It employ- to J . r . . . 



•*d in the ex- of alcohol of different degrees of purity, I ascertained with 



periaient?. ^ e g,- ea test care their specific gravities at the temperature 



of C0° F.^ taking that of water at the same temperature 



as 100000. I chose this temperature, that I might afterward 



the more easily ascertaiu the quantities of water, that each 



ought to contain, according to the tables constructed from 



the experiments of Mr. Lowitz. 



