Researches on Chemical Equivalence. 169 



fine effect, purely positive. The final action was at least as 

 strong as that of arnylene. My sample of this liquid was not 

 very clean ; and the initial extinction was far from pure. 



Butyl chloride was rather weaker than the last, and showed 

 no great increase of power with time. As a conductor, with- 

 out the jar, it gave a good restoration which was too abrupt 

 to be characterized ; with the jar and four or five turns of the 

 plate, it gave a very strong effect, purely positive by both 

 tests. My sample was not clean ; and the initial extinction 

 was quite impure. 



Amyl chloride, a very fine optical medium, giving perfect 

 initial extinction. As a nonconductor, it gave at first no trace 

 of effect in the polariscope, no spark from the prime conductor. 

 Tried then as a conductor without the jar, it gave a clear 

 restoration, too abrupt at first to be characterized ; but as 

 the experiment went on, the machine working at a moderate 

 rate, and discharges passing regularly through the cell, the 

 restorations in the polariscope rose very gradually in intensity, 

 till at last the effect was one of the finest that I had ever seen. 

 The liquid being now tried again as a non-conductor, the 

 prime conductor gave a spark more than half an inch long, 

 and the electro-optic action was magnificent, as fine apparently 

 as that of CS 2 . The effect was always strengthened by ten- 

 sion parallel to lines of force, and always weakened to ex- 

 tinction by the proper compression. 



[To be continued.] 



XIX. Researches on Chemical Equivalence. — I. Manganous 

 and Nickehus Sulphates. By Edmtot) J. Mills, D.Sc, 

 F.R.S., and J. H. Bicket*. 



THE following experiments were conducted with the view 

 of determining on what terms manganous and nickelous 

 sulphates might prove to be mutually equivalent; and the par- 

 ticular equivalence we have examined has been equivalent 

 precipitability of the sulphates, by sodic carbonate, from an 

 aqueous solution. 



I. Preparation of the Salts. 

 The pure manganous sulphate was prepared from the ordi- 

 nary commercial dioxide. The oxide was dissolved in hydric 

 chloride, the solution filtered and evaporated to dryness, the 

 residue dissolved in water, and excess of baric carbonate added 

 * Communicated by the Authors. 

 Phil. Mag. S. 5. Vol. 13. No. 80. March 1882. P 



