270 



Prof. E. J. Mills and J. Hogarth. [Jan. 23, 



The ratio of the working effect of sodic to that of potassic sulphate, 

 as calculated from the numbers given above, is 100*16 : 100, with a 

 probable uncertainty of 1*3 per cent. This is the mean value, reckoned 

 by the method of least squares, from the whole of the observations. 

 The rejection of the four experiments marked with an asterisk, which 

 differ somewhat widely from the rest, would give the ratio 99'53 : 100, 

 with a probable uncertainty of 0*73 per cent. ; while the probable error 

 of a single observation would then be reduced from 5' 02 to 2*4 per 

 cent. [Owing to the number of determinations made, any error in the 

 result is but very slightly affected by error in the ammonia estimation.] 



The conclusions which we think may fairly be drawn from these 

 numbers are : — 



(1.) That sodic and potassic sulphates have a well-marked influence 



on the reaction to which we have referred ; 

 (2.) That as more sulphate is added, the reaction is accelerated ; 

 (3.) That equal weights of sodic and potassic sulphates have as 



nearly as possible the same working effect. 

 The last conclusion may be otherwise expressed thus : — 

 If we represent our equivalent of potassic sulphate by a number, then 

 the equivalent of sodic sulphate is represented by the same number. 



II. " Researches on Chemical Equivalence." Part II. Hydric 

 Chloride and Sulphate; By Edmund J. Mills, D.Sc, 

 F.R.S., and James Hogarth. Received December 4, 1878. 



While carrying out our researches on lactin,* it struck us that use 

 might be made of it to compare the dynamical equivalents of acid 

 bodies. We accordingly selected hydric chloride and hydric sulphate 

 for the measurements in question, and prepared solutions of these 

 acids, containing respectively 73 grammes hydric chloride (2HC1), 

 and 196 grammes hydric sulphate (2H 2 S0 4 ) per litre. An experi- 

 ment was first tried with 5 grammes lactin and 10 cub. centims. of 

 the hydric chloride solution in a total volume of 70 cub. centims. At 

 a temperature of 17° C. there was no change of rotation in twenty- 

 four hours. In a second experiment a similar solution was raised for 

 an hour to 40° C, and then for an hour to 60° C. ; but without effect 

 on the rotatory power. The temperature of 100° C. was finally 

 adopted, the change at that point taking place at a rate admitting of 

 accurate measurement. The method of experiment was as follows : — 

 A measuring flask was made marked to contain 60 cub. centims. ; in 

 this were placed 50 cub. centims. of a 10 per cent, solution of lactin 

 (i.e., 5 grammes), the acid measured in, and the volume made up to 



* Post, p. 273. 



