DILUTE SOLUTIONS AT THE FREEZING POINT. 341 



the observations were recorded, full details from the laboratory note-book are given 

 on p. 342, for a set of measurements on sulphuric acid. This set is chosen as a fair 

 example of the usual degree of constancy among the measurements of resistance. It 

 is also shorter than any of the others, owing to the fact that sulphuric acid had been 

 investigated in the preliminary experiments, and could thus be disposed of in a fewer 

 number of observations. Four other solutions, stronger than any of this set, were 

 afterwards made up, and their resistances determined in .a Jena glass cell. The results 

 of these are included in the final table on p. 343. 



Sulphuric Acid (prepared at the Chemical Laboratory). A quantity of redistilled 

 sulphuric acid was taken, and the percentage of H 2 SO 4 found. Then a known 

 weight of S0 3 was obtained, and the calculated quantity of the sulphuric acid was 

 added to bring it up to 100 per cent. H 2 SO 4 . The acid was then cooled till crystals 

 separated, and the remaining liquid was drained away. This operation was repeated 

 four times, and finally gave crystals melting at -f-10'5 C. 



Four estimations of the concentration of the solution prepared were made with the 

 following results : 



Grammes of H2S0 4 



Weight of Weight of per gramme 



solution. BaS04 obtained. of solution. 



38771 1-6115 '01745 



35-4775 1-4780 '01749 



39-5265 1-6610 '01764 



89'2962 37240 '01751 



This gives '01752 for a mean value ; solution (a) had therefore a strength of 

 3*573 X 10~* gramme-equivalent per gramme of solution. For the dilute solution (b) 

 7'9880 grammes of (a) were diluted to a total weight of 155'80 grammes, giving a 

 strength of 1'832 X 10~ 6 gramme-equivalent per gramme of solution. 



