442 



A silicate of soda was formed by fusing together silica and carbo- 

 nate of soda, in proportions indicated by the previous experiments 

 i. e. 23 silica to 54 carbonate of soda = 3 1 soda. The fused mass 

 was crystallized. It was dissolved in water, and the solution evapo- 

 rated in vacua yielded a crystallized salt, which contained about 

 5 per cent, of carbonate of soda ; when this, calculated as the or- 

 dinary 10-hydrated salt, was subtracted, the silicate agreed nearly 

 with the formula NaO . SiO 2 + 7HO. A crystallized salt of like 

 composition was obtained when hydrated silica was dissolved in a 

 solution of caustic soda, the silica and soda being in the same 

 proportions, i. e. 31 : 23. In these experiments it appears, there- 

 fore, that in the process of solution and crystallization a portion of 

 soda is extruded. When exposed to a temperature of about 300 F., 

 nearly all the water was driven off from these salts, less than 1 per 

 cent, remaining. 



The fused silicate of lithia in like manner, when treated with water, 

 appeared to split up into different compounds. 



After guarding himself from drawing any decided inference from 

 the experiments recorded, the author concludes by observing that at 

 present he can see no alternative but to admit of more than one 

 equivalent for silicic acid (that is to say of more than one acid), the 

 value of which is determined by circumstances, such as the presence 

 of water and the nature of the base to which it is presented. The 

 existence of such different silicic acids has been already suggested by 

 chemists on different grounds, particularly by Ebelman and Laurent , 

 and lately by M. Fremy. 



II. Appendix to the Paper of Mr. W. H. BARLOW, " On an 

 Element of Strength in Beams subjected to Transverse 

 Strain/' &c. By PETER BARLOW, Esq., F.R.S. Received 

 March 25, 1857. 



A notice of this communication is given in the abstract of the 

 paper to which it refers (see antea, p. 432). 



