914 



STONE, ARTIFICIAL 



then pours in a mixture of chalk and Thames mud or Mersey mud burnt together. 

 This cement being poured into the mould, the whole is rammed together by falling 

 hammers, and as the mould is perforated, the water is forced out, and the resulting 

 stone is so hard, when removed from the mould, that it rings when struck. It will be 

 evident to those acquainted with hydraulic mortars and the application of concrete, 

 that this is only an improved concrete. The cost of production has been too great to 

 admit of the general introduction of this artificial stone. 



Eansome's Patent Siliceous Stone, being the most successful attempt to produce a 

 permanent stone artificially, requires further attention. 



After numerous failures, it occurred to Mr. Eansome that a solution of silica as a 

 cementing material would be superior to any other, and he accordingly started on the 

 inquiry after an easy method of producing a solution of flints. 



The accompanying illustration (fig. 1913) gives a sectional view of the apparatus 

 employed in preparing the solution of silica which Mr. Kansomc employs. 



1913 



A. is a steam-boiler, capable of generating a sufficiency of steam for heating tho 

 dissolving and evaporative vessels, and usually worked at a pressure of about 70 Ibs. 

 to the square inch. B is the upper lye-tank for dissolving the carbonate of soda. It 

 is supplied with steam by the pipes 1, 2, 3, communicating with the boiler. 



The first operation is to reduce the ordinary soda-ash of commerce to the condition 

 of caustic soda. For this purpose the ash is first dissolved in the tank B, the water 

 in which is heated by means of the perforated steam-pipe b. A quantity of quick- 

 lime is then added, and the mixture well stirred. The soda is by this means deprived 

 of the carbonic acid which it contains, by the quick-lime forming with it a carbonate 

 of lime. To ascertain when the lye is quite caustic, a small portion is taken out in a 

 test-tube, and a few drops of hydrochloric acid added. If there is no effervescence, 

 it may be assumed that the soda is entirely deprived of its carbonic acid, and is conse- 

 quently caustic, When the lime, now converted into chalk, has subsided to the 

 bottom of the tank, the clear supernatant lye is drawn off by the syphon 5, into the 

 funnel 6, leading into a closed vessel D, to prevent the carbonic acid of the atmo- 

 sphere combining with it, and destroying its causticity. When the lye has been drawn 

 off from B, the sediment remaining at the bottom of the tank is allowed to fall into 

 the lower tank c, by withdrawing the plug a, from the pipe A 1 . Any undissolved 

 crystals of the carbonate of soda which have been entangled among the particles of 

 the lime are now washed out and pumped back to the upper tank B, where it forms a 

 portion of the next charge. 



The clear caustic soda being contained in the closed tank n, has a further process of 

 depuration to undergo before it is ready to be used as a solvent for the flints. The 

 ordinary soda-ash of commerce is always more or less adulterated with a sulphate of 

 soda, which although an inert substance in itself, if allowed to remain in the cement 

 subsequently makes its appearance in an efflorescence on the surface of the finished 



