422 NOTICES OF THE MEETINGS [April 7, 
WEEKLY EVENING MEETING, 
Friday, April 7, 1854. 
Srr Cuartezs Fetiows, Vice-President, in the Chair. 
Rev. J. Bartow, M.A., F.R.S., Vice-President, and Sec. R. I. 
On Silica and some of its applications to the Arts. 
Sizica is one of the most abundant substances known. Quartz, 
common sand, &c. flint, chalcedony, opal, &c., and a variety of sand 
described by Mr. J. T. Way,* may respectively be taken as examples 
of crystallized and uncrystallized silica. Under all these forms 
silica is capable of combining with bases as an acid. Heat is how- 
ever essentially necessary to effect this combination, a combination 
of which all the well known silicates, whether natural, as feldspar, 
mica, clay, &c., or artificial, as glass, slags, &c. are the results. The 
common forms of insoluble glass are produced by the union of 
silica with more than one base. But, when combined with an 
alkaline base only, silica forms a soluble glass, the degree of solu- 
bility of which depends on the proportion which the silicic acid 
bears to this alkaline base . . . . This soluble silicated alkali (or 
water-glass) may be prepared by various processes. If sand 
be used, 15 parts of fine sand, thoroughly incorporated with 8 
parts of carbonate of soda, or with 10 of carbonate of potass, 
and one of charcoal fused in a furnace will: produce a silicated 
alkali which is soluble in boiling water. Messrs. Ransomes obtain 
this silicated alkali by dissolving broken flints in a solution of 
caustic alkali at a temperature of 300° Fah.¢ And, more recently, Mr. 
Way has observed that the sand which he has described, will com- 
bine with caustic alkali at boiling heat, also producing a water-glass. 
This water-glass has been applied to several important purposes, 
three of which were specially noticed. 
I. To protect building-stones from decay. The stone surfaces of 
buildings, by being exposed to the action of the atmosphere, become 
liable to disintegration from various causes. Moisture is absorbed 
into their pores. The tendency of their particles to separate, in con- 
sequence of expansion and contraction, produced by alternation of 
temperature, is thus increased. Sulphurous acid is always present 
in the atmosphere of coal-burning cities, and cannot but corrode 
the calcareous and magnesian ingredients of oolites and dolomites. 
* Quarterly Journal of Chemical Society, July 1, 1853, and Journal of Royal 
Agricultural Society, Vol. xiv. Part 1. 
+ Report of a communication made to the Royal Institution by Professor 
Faraday, May 26, 1848. Vide Atheneum, June 17th, 1848. 
