268 



Prof. E. J. Mills and T. U. Walton. [Jan. 23, 



The following Papers were read : — 



I. " Researches on Chemical Equivalence. Part I. Sodic and 

 Potassic Sulphates." By Edmund J. Mills, D.Sc, F.R.S.. 

 " Young " Professor of Technical Chemistry in Anderson's 

 College, Glasgow, and T. U. Walton, B.Sc. Received 

 October 16, 1878. 



The conception of a chemical equivalent as employed in these 

 researches corresponds to a definition first given* by one of us, viz., 

 that the chemical equivalent of a body is that weight of it which does 

 the unit of work. We do not therefore use the term in its ordinary 

 sense; as, for example, when it is said that H is "equivalent" to CI, 

 Na, &c. 



The following experiments were arranged with the view of determin- 

 ing the effect of potassic and sodic sulphates on the rate of formation of 

 ammonia, when nascent hydrogen is made to act on potassic nitrate. 

 Judging from their behaviour in other cases, it was expected that in 

 this instance, also, their action would be one of retardation. Experi- 

 ment, however, has proved the reverse, on the whole, to be true. 



The extremely delicate nature of the reaction, which is liable to be 

 spoiled by the accidental falling in of a single speck of dust, or by 

 slight variation of temperature, or unequal exposure of the different 

 solutions to light, rendered the attempt to measure the effect a matter 

 of peculiar difficulty. 



At first, common sheet zinc, thoroughly cleansed from grease, was 

 placed in a solution of potassic nitrate and hydrate, and the amount of 

 ammonia formed during periods varying from twenty-four hours to one 

 week was measured. But the results were very irregular and unsatis- 

 factory. Galvanic couples seemed to be established at certain points 

 on the surface of the zinc, probably due to the presence of iron or lead 

 as impurities. Thin zinc foil was next tried, but with little better 

 result ; neither were any alterations in the shape or disposition of the 

 foil attended with success. Fresh experiments were also undertaken 

 with sodium amalgam instead of zinc and potassic nitrate ; but the 

 action, though rather more uniform, was still very uncertain. It was 

 found impossible to obtain a perfectly homogeneous solution of sodium 

 in mercury, entirely free from sodic oxide and hydrate ; and this 

 seriously impaired the accuracy of measuring out the amalgam. 



The only plan which was found to give results at all comparable 

 with each other, was using zinc amalgam and potassic nitrate. The 

 experiments were performed in wide-mouthed glass-stoppered bottles 

 of cylindrical shape, having an internal diameter of 60 mm., and a 

 total capacity of 315 cab. centims. Each bottle contained 1 grm. 

 * " Philosophical Magazine," [5], i, 14. 



