OSI 



PHILOSOPHICAL TRANSACTIONS. 



[anno 1790. 



In order to deduce the specific gravities from 



TABLE II. 



iVeights and Sptcific Gravities of Dis- 

 tilled Water. 



the numbers in the preceding table, it was ne- 

 cessary to weigh distilled water in the same 

 vessel. This Mr. Gilpin did, in the same 

 manner as before, at the different degrees of 

 heat ; and the result of his experiments is deli- 

 vered in the annexed table, where the first co- 

 lumn shows the heat, and the 2d gives the 

 weight of the water, at that temperature, con- 

 tained in the bottle. 



There would be 2 methods of computing the 

 specific gravity, at the different temperatures, 

 from these numbers ; one, by taking the weight 

 of the water, at the particular temperature in 

 question, for the standard ; and the other by 

 fixing on one certain temperature of the water, 

 for instance 6o°, to be the standard, with its bulk at which that of the spirit at 

 all different degrees shall be compared. The latter method was preferred, though 

 not the most usual, because it shows, more readily and simply, the progression 

 observed in the changes of specific gravity, according to the heat and strength 

 of the mixture. This method however rendered it necessary to make an allow- 

 ance for the contraction and expansion of the bottle used for weighing the 

 liquors, according to the deviation of their temperature from 6o°, either below 

 or above. To obtain this correction, the expansion of hollow glass was taken 

 from General Roy's experiments in the 75th volume of the Philos. Trans, as 

 .0000517 of an inch on a foot for every degree of heat; whence its effect, in 

 enlarging the capacity of a sphere, was computed, and the resulting correction 

 added to the weight of the liquors in heats below 6o°, and subtracted from it in 

 heats above. On the same account a 3d column is given, in the preceding 

 table, to show the specific gravity of water at the different temperatures, its 

 weight at 60° being taken as the standard. 



Another correction also became necessary, on account of the part of the 

 stem of the thermometer which was not immersed in the liquor. This instru- 

 ment made by Ramsden, had its ball .22 of an inch in diameter, and its stem 

 13 inches in length. From the ball to the commencement of the scale 3.6 

 inches of the stem were bare, and then the scale began, which reached from 15 

 to 110°. The part of it particularly used in these experiments, namely, from 

 30° to 100°, measured 6.82 inches. The scale was made of ivory, and carried 

 divisions to every 5 th of a degree, the quarters of which could be readily esti- 

 mated ; so that the instrument could be read off to 20ths of degrees. When 

 the thermometer was immersed in the weighing-bottle, the liquor reached up 



