1879.] 



On Chemical Equivalence. 



269 



potassic nitrate, 1 grm. potassic hydrate (prepared from the sulphate 

 by means of baryta water), and a quantity of anhydrous alkaline 

 sulphate, varying from to 1 grm. ; the whole being dissolved in 

 150 cub. centims. of distilled water, very free from ammonia. The 

 reagents had been carefully purified. 30 cub. centims. of amalgam, 

 prepared by dissolving 10 grms. zinc in 10 kilogs. mercury, were then 

 added, and the " system " was preserved from dust and light. After 

 twenty hours, the amount of ammonia was estimated by Nessler's 

 method. Traces of this substance were occasionally present in 

 the solutions employed, and a corresponding correction had to be 

 made. In every experiment, nine solutions were prepared at the same 

 time — three free from sulphate, three containing sodic sulphate, and 

 three potassic sulphate ; and the mean of each three was taken as the 

 true value for that particular experiment. Fifteen comparisons of 

 each of nine solutions, arranged in this way, were made with different 

 quantities of sulphate. The temperature was taken at the beginning, 

 in the middle, and at the conclusion of the experiment ; the tempera- 

 ture at night being registered by one of the automatic thermometers 

 sold by ISTegretti and Zambra. Owing to the extreme delicacy of the 

 reaction and the slight causes which suffice lo interfere with it, the 

 numbers obtained from single experiments are not sufficiently reliable 

 to measure the precise amount of change caused by varying the 

 quantity of alkaline sulphate. Every comparison, however, though 

 made with a different weight of sulphate from that employed in the 

 others, involved equal weights of potassic and of sodic sulphate ; and 

 hence the relative effect of those two bodies has been very clearly 

 approximated to. 



The following table gives a summary of the observations made : — 



G-rm. 

 sulphate 

 added. 



Mean 

 temp. C. 



G-rm. ammonia 

 formed in the 

 blank (150 c.c.). 



Blank. 



Ratio. 



Experiment 

 with sodic 

 salt. 



Experiment 

 with potassic 

 salt. 



o-i 



18-4 



-0000432 



100 



102-2 



99-5 



#0-1 



14 6 



-0000135 



100 



99-1 



88-8 



0-2 



13 -4 



-0000424 



100 



100-1 



103-2 



0-3 



16-4 



-0000459 



100 



79-3 



79-5 



03 



14-1 



0-0001200 



100 



103 9 



102 -0 



0-4 



15-6 



-0001350 



100 



105 -4 



109-5 



*0'5 



15 6 



0-0000655 



100 



108-5 



97 -7 



*0-5 



16 3 



-0000493 



100 



110-1 



96 -6 



0-6 



18 -4 



-0000391 



100 



99-5 



105 -1 



0-6 



22-6 



-0000445 



100 



109-7 



107-8 



7 



17-1 



0-0000431 



100 



104-8 



104-8 



0-8 



15 -2 



-0000670 



100 



113 -8 



113 -2 



0-9 



15 -4 



-0000679 



100 



107-1 



113-4 



•J.-0 



12-3 



0-0000359 



100 



111-1 



129-8 



10 



17 -0 



-0000456 



100 



121-7 



U4-9 



