m 



ON LATENT HEAT, 



Expei'iments on the Latent Heat of Lead. 



In thefe experiments I have, by accident, loft the notes of 

 the determination of the weight of the veflfel emploj/ed in all 

 but the two firft inftances : notwithftanding which it may be 

 fairly inferred, that the mean latent heat of lead is about 150'', 

 a quantity certainly unexpeftedly fmall, and which, in many 

 more experiments than thefe related, I was at pains to exa- 

 mine, without being able to difcover any material inaccuracy* 

 In the fecond experiment, where a little fte^m was formed, I 

 afcertained the lofs to be four grains. If thefe four grains be 

 fuppofed, as in the cafe of bifmuth, to contain 470^* of heat, 

 the computed addition to the latent heat of lead will be 20^.3, 

 making in all a little more than 162**. This is certainly a very 

 peculiar and unexpe6led quality of this metal, 

 Experiments on The only other fubflance which I have fubmitted to exa- 

 folphur. mination for (he purpofe of afcertaining its caloric of fluidity, 



is fulphur. The melting point of fulphur is commonly ftated, 

 in elementary works, to be at 212° : But that this is not accu- 

 rate any one may convince himfelf, by immerling a quantity 

 of fulphur in boiling water, where it remains altogether unal- 

 tered. By every trial which I have been able to make, I 

 am convinced that the fufion of fulphur takes place about the 

 temperature of 226®, I fay about, becaufe the communica- 

 tion of heat among the particles of fulphur is very flow, and 

 the thermometer is often encrufled with folid fulphur, which,. 

 jTome how or other, certainly cools below the liquid in which 

 • it is immerfed. In experiments for afcertaining this point, 

 the thermometer ought to be kept in conftant motion. The 

 refults of my experiments for finding the latent heat of fulphur^ 

 are ibted in the following table* 



Experiments 



