54G MR J. Y. BUCHANAN ON 



solution. If the boiling temperature of the stronger solution be t v and steam be passed 

 through it until this temperature has fallen to t 2 , the temperature of steam condensing 

 on pure water being T, and if the quantity of water in the stronger solution be W v and 

 in the weaker W 2> then wo should have 



whence 



W 1 (* 1 -T)=W 2 (« 2 -T), 



the values of \N(t — T) are constant, which is the characteristic of Blagden's law, whether 

 applied to freezing or boiling. The deviations from Blagden's law in freezing and in 

 boiling solutions may be attributable to some deviation from the law that the capacity 

 for heat of a saline solution is the capacity for heat of the water which it contains. It 

 is easy to obtain from the values of W(t — T) in Table IV. what must be the specific 

 heat of the saturated water which would make W(t — T) constant. 



Table V. gives for dilute solutions what Table IV. gives for strong solutions. As the 

 values of (t — T) are not exactly the same for each salt, the relations of t — T and 

 W(£ — T) were expressed by curves and the values of W(t — T) taken from them 

 for the same values of t — T for every salt. These values are given in Table VI. 

 In all the experiments of Table V., exactly one-twentieth of a gramme-molecule of salts 

 was taken, and the weight was exact to the nearest milligramme, and the experiments 

 were made in every way alike. Table V. contains no mixtures ; on the other hand, 

 some simple salts are included which are not found in Table IV. They are LiCl, RbCl, 

 CsCl, KI, KBr, KN0 3 , and AgN0 3 . Both the KbCl and the CsCl were " spectroscopi- 

 cally pure," and the caesium salt was quite pure. The rubidium salt, however, contained 

 sulphate, and it is struck out in Table VI. The detailed discussion of these results, as 

 well as of those in Table IV., must stand over to the second part of this paper, but one 

 or two facts ma)'- be pointed out. In the case of salts for which the values of W(t - T) 

 diminish as dilution increases, a minimum is reached when t — T is something between 

 07° and 1*0° C, after which it increases in all so that for values of t — T between 0'5" 

 and 1*2° the values of W(t — T) for all these salts is practically constant, and they follow 

 Blagden's law. In the case of nitrates W(£ — T) generally increases with dilution, and a. 

 minimum, if it exist, would have to be sought in solutions saturated under high pres- 

 sure. Strontium nitrate is an exception ; it has a minimum at 1*0° C. 



In Table VII. will be found the values of^>, the vapour tension of pure water at the 



. . /» — P\ 



temperature (t) of the boiling brine, the relative reduction of this tension I — j pro- 

 duced by the salt in solution, and the product of this ratio into the weight of steam 

 condensed (W). The discussion of the contents of this table is deferred. 



The discussion of the observations on mixtures is also deferred. It involves a very 

 large amount of arithmetical work, which will take some time. The behaviour of mixtures 

 is extremely interesting. In Table IV. we have examples of two distinct types. Of the 



