48 The Philippine Journal of Science i9i8 



subject as a whole shows little progress. One reason for this 

 is that in carrying out investigations no definite plan of attack 

 has been followed. 



Because of the complex nature of cements and the great dif- 

 ference in physical and chemical properties, it is believed that 

 complete uniformity of results is not possible, but that qualitative 

 agreement may be hoped for. 



The general effect of all the electrolytes studied is to lessen the 

 tensile strength and to modify the set. 



On the basis of their effect on the set, the electrolytes may 

 be divided into two groups. The members of one group cause 

 a retardation of the set up to a certain concentration and then 

 cause an acceleration. The members of the other group cause 

 a retardation of the set which increases with the increase of the 

 concentration, until the set is practically destroyed. 



With the salts investigated in this paper the positive ion is 

 more important than the negative in determining the effect of 

 an electrolyte on cement. There is no well-established rela- 

 tionship between this effect and the solubility of any calcium 

 compounds that may be formed. More extensive work will be 

 necessary before the effect of an untried electrolyte can be 

 predicated. 



