Atomic Volume and Specific Gravity. 46S 



Chloride of Magnesium, MgCl + 6HO = 10-2'16.— Millon 

 has lately described this salt as containing 6i atoms of water ; 

 but, as we have not been successful enough to obtain this hy- 

 drate, we retain the old formula. 25*54' grains, or the fourth 

 of an equivalent, dissolved in 1000 grains of water at 53°, 

 with an increase of 14"0. 



Mg CI + 6HO, vol. in solution = 56*0. 



The same quantity, 25*54 grains, gave, in four experiments, 

 respectively, 16*5; 16*0; 16*4; 16*5. 



Sp. gr. 

 I. Mg CI + 6 HO volume of salt 66*0 ... 1*548 



II 64-0 ... 1-595 



111 65*6 ... 1-557 



IV 66;0 ... 1-548 



Mean . . 65*4 ... 1*562 



The salts now examined are not calculated, on account 

 of the deliquescent character of several of them, to produce 

 absolutely accurate experimental results; but, notwithstanding 

 this circumstance, the determination of their volumes is suffi- 

 ciently uniform to indicate the theory. The actual volume 

 observed for each of the salts in solution, when divided by 9, 

 the atomic volume of water, yields as the quotient the same 

 number as that representing the atoms of water in the salt. 

 Hence it is quite certain that the salts now described dissolve 

 in water without adding to its bulk more than is due to the 

 liquefaction of the water in chemical combination with them. 



The volumes of the salts in their solid state possess a num- 

 ber considerably higher than that representing the liquid vo- 

 lume, but affect a divisor, which is the same for all the salts, 

 allowing for errors of experiments, or for alterations caused 

 by incidental circumstances. This divisor is a number either 

 equal or approximating to 11. When the volumes of the 

 salts in the solid state are divided by this number, the quotient 

 represents the number of atoms of water attached to the salt. 

 The most natural view of this circumstance is to suppose that 

 water in combination as a solid with a salt possesses a higher 

 volume than liquid water, just as in the case of ice. If this 

 view be correct, the atomic volume of the salts described is 

 the same in the state of a solid as when in solution, the only 

 difference being, that in the one case the volume is expressed 

 by liquid, in the other by solid water. In this case, however, 

 water in combination with a salt does not possess the same 

 volume as ice, which, according to our experiments, detailed 

 in another part of this paper, has a volume of 9*8, and not of 

 a number approaching to 11. 



