Alomic Volume and Specific Oravitij. 



457 



without reference to the density or temperature 0(fijtl»e soll>i^ 

 tion oa which he^operated. ; '"- ^ ii 



b9ifK)VB'j#rid o«^ ^f In the experiments about to be described, 

 the apparatus for estimating the volume of 

 bodies when dissolved, consisted of a glass 

 bulb, to which a stem was attached. The 

 bulbs varied in capacity from 1000 to 4000 

 grains of water, and the diameter of the stem 

 was from one-eighth to one- sixteenth of an 

 inch, according to the character of the ex- 

 periment. In the bulbs employed for ordi- 

 nary purposes, each grain ot water occupied 

 about a quarter of an inch in the stem, and 

 as the graduation was made in grains of water 

 at 60°, the experiment could be made to the 

 tenth of a grain of increase in volume. In 

 every case care was taken that the salts used 

 were rigidly pure, and in their proper state 

 of hydration. The distilled water employed 

 to dissolve them was deprived of air by long- 

 continued boiling, and preserved for use in 

 stoppered bottles. The salt was introduced 

 by a tubulure in the side of the bulb in the 

 following manner. The bulb was filled with 

 water until it reached a fixed point in the 

 stem, when it was reclined and the stopper 

 removed. A weighed quantity of salt was 

 then introduced by a dry funnel, and the 

 stopper re-inserted, care being taken that no 

 air was admitted during the operation; the 

 increase in the stem, after the salt was dis- 

 solved, gave the volume of the quantity of 

 salt used in the experiment. It was found by 

 repeated trials that no loss of volume or error 

 was occasioned by the moistening of the tube 

 during the time it was in the reclining pos- 

 ture, for the precaution was always taken to 

 moisten the walls of the tube pz'evious to the 

 experiment. It is evident that the volume occupied by a salt 

 in solution must be modified by the position of the point of its 

 maximum density. Despretz has shown* that the tempera- 

 ture at which solutions are most dense becomes lower in pro- 

 portion to the quantity of matter held in solution. It is also 

 known, from the experiments of Dalton and others, that from ., 

 the point of maximum density to about 30° above or below it, 

 * Annates de Ckimie, vol. Ixx. 1839, p. 81. 

 P/iil. Macr. S. 3. Vol. 27. No. 182. Dec. 1845. 2 H 



