CHEMISTRY — NOYES, RICHARDS. I 55 



ing report, which consists in determining the increase produced in 

 the conductivity of the salt by the addition to it of one of its hydro- 

 lytic products, acetic acid or ammonium hydroxide. The results 

 obtained show that the ionization of both the acid and base dimin- 

 ishes greatly with rising temperature, while that of water increases 

 enormously between i8° and ioo° and largely between ioo° and 156 . 

 Thus the value of the ionization-constant of water (the product of 

 the concentrations of the free hydrogen and hydroxyl ions present 

 in it), which had been found to be 0.6 X io~ 14 at 18 by previous 

 investigators, is shown by these new measurements to be 49 X io~ u 

 at ioo° and 221 X io~" at 156 . These two opposite variations in the 

 ionization of weak acids and bases on the one hand and in that of 

 water itself on the other reinforce each other in producing increased 

 hydrolysis at high temperatures and make it an important factor even 

 in the case of salts which scarcely exhibit it at all at ordinary tem- 

 peratures. This is well illustrated by ammonium acetate itself, which 

 at o. 1 normal concentration is hydrolyzed 0.4 per cent at 18 , 4.8 per 

 cent at ioo°, 18.3 per cent at 156 , and about 50 per cent at 218 . 

 The third research on electrical transference in aqueous solutions 

 has been prosecuted in anew direction, with the view of determining 

 the extent to which ions are hydrated. The hydration of substances 

 in solution is one of the most important, as well as one of the most 

 difficult, of the unsolved problems connected with the theory of 

 solutions. In the case of ions it is possible to determine to what 

 extent water migrates with them by making accurate transference 

 determinations in the presence of a non-migrating substance, like 

 cane-sugar. During the past six months the details of an experi- 

 mental method have been worked out, by which it is hoped to obtain 

 conclusive results in regard to the hydration of some of the more 

 important ions. 



Richards, Theodore W. t Harvard University, Cambridge, Massa- 

 chusetts. Grant No. 240. Investigation of the value of atomic 

 weights, etc. (For previous reports see Year Book No. 2, p. xxxii, 

 and Year Book No. 3, p. 112.) $2,500. 



Abstract of Report. — Five researches were conducted under the 

 direction of Prof. Richards with the support of this grant, as follows : 

 ( 1 ) An investigation of the atomic weights of sodium and chlorine 

 carried on with the assistance of Dr. Roger Clark Wells. This inves- 

 tigation has been finished, with satisfactory results of unusual com- 

 pleteness, and the results have been published in a monograph of 70 

 pages (Carnegie Institution Publication No. 28). The final results, 



