4<» 



ON LATENT HEAT. 



175 > t»n 5c 



Ijtpcrlments 

 made by the 

 aatbor* 



The veiTels. 



fame experiments to prove that the fluidity of alum, fulphar, 

 and fome metals, was accompanied wilh an abforption of latent 

 heat ; but I believe he made no attempts to afcertain the pie- 

 cife quantity. In Dr. Black's lectures we are informed, that 

 Spermaceti Dr. Irvine found the latent heat of fpermaceti to be 143®, of 



145 , ees wa^x ^^^, ^^^ ^^ ^ 173**, and of tin to be 500^. From the very 

 imperfed notes which I poflefs of the methods ufed to deter- 

 mine the two former, I believe that the 145° are meafured by 

 the capacity of fluid fpermaceti, and the 175*^ by that of fluid 

 wax: But of this fubjed I will take another opportunity to 

 treat more amply. I am perfedlly ignorant of every circum- 

 fiance regarding the latent heat of tin as determined by my 

 father, having been unable to find any notes of his experi- 

 ments for determining this point. 



During the courfe of the prefent year I have turned my at- 

 tention a little to this fubje6l, I mean to the inveftigation of 

 the quantity of latent heat necefltrry for the fufion of various 

 bodies. I was perfuaded that an addition to our knowledge of 

 latent heat would at leaft increafe the ftoreof fadts, and might 

 perhaps give rife to fome improvement or correction of theory. 

 The veflels which I employed in all my experiments were 

 Florence flalks, ot which the neck was cut off. In thefe the 

 water made ufe of was contained, and the veflfel was fupported 

 on a flight wo®den ftand, which prefented a very fmall furface 

 to abftrad heat from the materials. The orifice at the fuperior 

 part of the veflel, was in general not more than fufficient to 

 permit the ready introduction of the fluid examined ; probably 

 from an inch and a quarter in diameter to a little more, fo that 

 a very fmall furface of the water was expofed to the ak. The 

 weight of the glafs was in all cafes previoufly afcertained. 

 Thefe circumflances being premifed, I proceeded as follows: 

 The firft fubftance which I fubmitted to examination was 

 *'^^ll'.'ff".'^"u bifmuth. The melting point of this metal was, by the ther* 



ot fluid bifmuth , ^ . . . . 



(or the numder mometer which I ufed, 480". This is fo near the point found 

 of degrees ^ by my father, to wit 476**, that I ftiall confider his determina- 

 anv'quantlty of tion as correCl, as he combined and compared the different 

 blitnuth would, ways of computation and obfervation, and I know the ther* 

 gfvesou^In con- "IOmeter which he ufed to have been made with confiderable 

 gelation, raife an care. Into a glafs veflel which weighed 411 grains, I put 

 Sl?h'"rom*'^''^2^^' ^''a^"^ of water, of the temperature of 62^. I then re* 

 beneath the moved from the fire a quantity of fluid bifmuth. I waited till 



hot zing point of jt 



iba aieta!). 



Determination 



