CHAP. XII.] CAVENDISH PAPERS. 401 



p 



gives a (velocity) 2 which could also be got from the 



p 



of the vapour (a different one). 



Then this gives also a standard temperature ; all that 

 we want is to get pure water. 



To THE SAME. 



Glenlair, 23d August 1877. 



I have been copying Cavendish on the resistance of 

 electrolytes. If there is any one who would try a few of 

 them roughly in the U tube, it might be interesting to com- 

 pare with Cavendish's results. For weak solutions Kohl- 

 rausch may be referred to. 



Sea Salt (Chloride of Sodium?) 

 Experiments in January 1781. 



Watered to Resistance. Resistance 



1 of Salt. X quantity of Salt. 



Saturated sol. 3'78 1 



12 1-91 -602 



30 3-97 -500 



70 8-8 -475 



143 15-75 -416 



1000 93-02 -352 



20,000 18-23 -345 



Salt in 20,000 conducts about 7 times better than dis- 

 tilled water. 



Salt in 69 of water conducts 1*97 times better at 

 105 F. than at 58J. 



If Professor Liveing is in Cambridge, could you ask him 

 to put me in the way of finding the best book on chemistry 

 for the year 1777, so as to obtain the equivalents and the 

 names of salts used by Cavendish ? 



The numbers in the first columns are the quantities 

 which were equivalent to the " acid " in solution of 1 of salt 

 in 2 9 of water. 



2 D 



