204 



BUILDING MATEKIALS. 



nitrate of silver fails to detect chlorine in the 

 liquid. This solution remains fluid for some 

 days, but it ultimately gelatinizes. Of these 

 two methods, the former gives the silicious 

 solution in the greater strength. When such 

 solution, thus prepared, is applied with a clean 

 brush once or oftener over the surface of chalk 

 or dolomite, Mr. Crookes states that a process 

 of hardening occurs, which goes on increasing 

 for several days, while, owing to the depth of 

 penetration, and to there being no soluble or 

 efflorescent compounds to be removed, there 

 appears a strong probability of permanent pro- 

 tection by means of this silicious impregnation 

 to the stones so treated. (It must be added, from 

 other sources, that upon actual test of the pure 

 solution of silica for preserving stone, made in 

 England, it was found that the solution too fre- 

 quently gelatinized mainly on the surface of the 

 material, drying and scaling off, and chipping 

 the surface in so doing. It cannot, therefore, be 

 recommended, as is done by Mr. Fleury, for 

 preserving building stones, and more especially 

 not for decaying monuments. Of the other 

 uses suggested by the writer named, and which 

 will be mentioned, some may prove of real 

 practicability and value.) 



The first of the proposed applications of the 

 hydrated silica being set aside, among the 

 others are, briefly, the following : 2, The for- 

 mation, by admixture in due proportions with 

 other cheap materials, as lime, clay, sand, &c., 

 of artificial building and other stones ; 3, The 

 application of the solution to wood, so as to 

 render it comparatively indestructible, and fire 

 and water proof; 4, The mixing of the solution 

 with certain colors used by painters, and form- 

 ing silicated colors, such as have lately been 

 employed by Kaulbach and by many other 

 painters of frescoes, German, French, and Eng- 

 lish, and which (chemical analysis showing 

 that the frescoes at Herculaneum and Pompeii 

 were of such character) appear to have the 

 quality of resisting the change usually caused 

 by time ; 5, The formation, by mixture with 

 certain materials, of a durable artificial marble, 

 susceptible of beautifully variegated coloration ; 

 6, Combination with certain organic substances 

 to form many articles for which a plastic ma- 

 terial or composition is suitable, as certain 

 parts of machinery, furniture, &c. ("Journal of 

 the Franklin Institute," January, 1862.) 



Messrs. Bartlett, Bros. & Co., of Camden 

 Town, Eng., propose ("Chem. News", No. 101) 

 as a preservative material a combination of sili- 

 cate and aluminate of potash, the latter prepared 

 from a fused compound of alumina and potash, 

 and dissolving readily in water, with not more 

 than two per cent, of free potash. "When sili- 

 cate of potash, sp. gr. 1.250, and this alumi- 

 nate of potash, sp. gr. 1.200, are mixed, instan- 

 taneous decomposition takes place, the result a 

 solid mass, consisting of silicate of alumina, 

 and some free potash. The mass hardens with 

 extraordinary rapidity. The solutions being 

 of somewhat less specific gravity, so that, mix- 



ed, they shall be of sp. gr. 1.150, the result of 

 the combination lasts as a solution about 10 

 hours ; but formed at or evaporated to about 

 sp. gr. 1.200, it solidifies immediately. The 

 product of the combination of the materials 

 named, is declared to resist dilute sulphuric and 

 hydrochloric acids. 



The defect referred to above in the process 

 suggested by Mr. Crookes, with pure solution 

 of silica, Mr. Church thinks he has obviated by 

 his method, which consists in applying along 

 with the silica solution, usually first, but some- 

 times second, a solution of baryta (oxide of 

 barium). The result he states to be the depo- 

 sition within the interstices of the stone so 

 treated of the insoluble and unalterable silicate 

 of baryta, no other materials accompanying 

 these, so that no soluble or otherwise injurious 

 salt can be formed. By this process he con- 

 siders that porous stones are necessarily made 

 harder, and less subject to atmospheric influ- 

 ence ; that brick, terra cotta, &c., may be made 

 nearly water-proof ; and that articles moulded 

 from plaster of Paris are greatly improved in 

 appearance and durability. The application, 

 as proposed by others, of a silicate of soda and 

 chloride of barium, results in production of sili- 

 cate of baryta and chloride of sodium, the lat- 

 ter of which, washing out by rain, Mr. Church 

 concludes, must injure the stone in respect to 

 durability and appearance. 



The process of Mr. Frederick Ransome, how- 

 ever, involving a principle nearly similar to that 

 just stated, has received high commendation, 

 and, among other authorities, by Prof. Ansted 

 before the recent meeting of the British Asso- 

 ciation. Ransome's process consists in a de- 

 posit or formation within the substance of 

 stones sufficiently porous, and whether natural 

 or artificial, of a silicate of lime. The absorb- 

 ent block or mass is first saturated, so far as 

 may be, with a solution of silicate of soda ap- 

 plied to the surface, when this is followed with 

 an application of solution of chloride of cal- 

 cium : as the latter penetrates so as to come in 

 contact with the former substance, a double 

 decomposition takes place, the results being an 

 insoluble silicate of lime, and a soluble chloride 

 of sodium, the latter of which can be mainly 

 washed away at once, or left to be removed 

 gradually. Mr. Ransome formed in moulds 

 small blocks of sand wet together by applying 

 the liquid silicate of soda, and then hardened 

 these by dipping them in the solution of chlo- 

 ride of calcium. The result was the formation, 

 almost instantaneously, of a perfectly compact, 

 hard, and apparently durable solid. In this 

 and other ways, the inventor had employed the 

 process in preparing artificial stones. Some 

 of these are already in use upon the Metropoli- 

 tan Railway. They are cheap, can be made on 

 the spot where needed, of almost any rubbish 

 or material at hand, and of any desired form 

 and size. A bar of one of these artificial 

 stones, 4 square inches in section, and over 8 

 inches between supports, sustained 2,122 Ibs. ; 



