2 Jackson and Rich, Solubility of Lead Glasses. 



has received a great amount of attention ; and much 

 experimental work has been carried out, with the view to 

 reduce the solubiHty to such a degree that the glazes 

 should be innocuous to the workers coming in contact 

 with them. 



According to Zulkowski a glass which shall be capable 

 of resisting chemical agents must approach a trisilicate ; 

 and the insolubility appears to be developed by the 

 presence of dibasic oxides, and may be due to the coupling 

 of two polysilicates by a dyad metal as 



^O.Si.O.O.SiO.O.Si.O.O.R' 



^O.SiO.O.Si.O.O.Si.O.O.R' 

 RO.eSiOa.R.'O. 



The use of a trisilicate for Pottery purposes is, for 

 practical reasons, impossible ; hence it appeared important 

 to determine the solubility of certain compound disilicates, 

 which it is proposed to employ. 



It appeared to us necessary to determine whether 

 there exist factors, other than the chemical composition, 

 which may influence the solubility of lead fritts in dilute 

 acid, and also to examine the extent of the action of any 

 such factors. The following is an account of experimental 

 work carried out with these ends in view. 



I. Tlie Effect of Fineness on the Solubility of Lead Fritts. 



In the first place, solution being possible only from 

 the surfaces of non-porous particles, it seemed that the 

 solubility might be affected by the extent of surface 

 exposed to the solvent, or in other words, by the degree of 

 fineness ; for it can be readily shown that the surface of 

 unit mass of spherical particles varies inversely as their 

 mean diameter, and we may consider that the glaze 

 particles are, or approximate to, spheres. 



