WORK OF J. N. PEARCE. 61 



From the dissociation we calculate the true molecular lowering which would be 

 produced by the dissolved substances if there were no hydration; and if there is no 

 hydration these two values for the molecular lowering should be equal. 



The calculated lowering, divided by the observed lowering and multiplied by 1,000, 

 gives the amount of water present playing the role of solvent, if the quantity of the 

 substance present is dissolved in 1,000 grams of water. 



The difference between this amount of water and 1,000 grams givesthe amount of 

 water which is combined with the dissolved substance in the solution in question. 



Knowing the number of grains of water which are in combination with the dis- 

 solved substance, the number of gram-molecules of water combined with the sub- 

 stance is obtained by dividing this number by 18. If we divide this value by the 

 concentration in terms of normal, we obtain the number of molecules of water which 

 are in combination with one molecule of the dissolved substance when the amount of 

 substance present in 1 liter of the solution is dissolved in 1,000 grams of water. 



In the various tables of data the symbols have the significance already stated. 



In the specific-gravity tables, W so i is the weight of 1 liter of the solution; W talt 

 is the weight of the salt contained in 1 liter of the solution ; and Wu,o is the weight 

 of water contained in 1 liter of the solution. The percentage correction is the correc- 

 tion which must be applied to the freezing-point lowering in order to refer it to 1,000 

 grams of the solvent, instead of the amount of water that is actually present in 1 

 liter of the solution in question. 



In the hydrate tables, m is the concentration in gram-molecules per liter; a the 

 approximate dissociation as measured by the conductivity method; L the theoretical 

 molecular lowering of the freezing-point referred to 1,000 grams of solvent; A/m the 

 observed molecular lowering; L' the corrected molecular lowering; M the number 

 of gram-molecules of water in combination with the solute; and H the number of 

 gram-molecules of water combined with one molecule of the salt at the concentration 

 in question. 



CALCIUM CHLORIDE. 



The data for calcium chloride are given in table 45. 



The value of /Xoo is surprisingly low when compared with that obtained by West 1 

 and by Bassett. 2 It is however, very nearly equal to that obtained by Jones and 

 Stine. 3 



A study of table 45 leads us to the following conclusions : The theoretical molec- 

 ular lowerings, as given in column L, decrease regularly with increase in concen- 

 tration, while the corrected observed molecular lowerings, as seen in column U, 

 decrease rapidly, reach a minimum at 0.1 normal, and then increase with increase 

 in concentration. 



It is very probable that the value of L' for 0.01 normal is too large, but, owing to. 

 the inaccuracy of the method for such dilutions, this is unavoidable. 



It will be seen from column M that the amount of water which has entered into 

 combination with the dissolved salt also passes through a minimum between 0.075 

 normal and 0.10 normal the same concentration which gives the minimum molec- 



'Amer. Chem. Journ., 34, 393 (1905). mid., 33, 547 (1905). mid., 39, 331 (1908). 



