Contributions to Experimental Chemistry, 373 



speedily renders the fluid colourless prior to ebullition ; but, 

 after boiling, a continued current of this gas is requisite to pro- 

 duce the same effect. If a solution of one proportional of 

 chloride of iron be added to a cold solution of one and a half 

 proportional of silicate of soda (in about forty proportionals of 

 water), a gelatinous precipitate of silicate of iron is formed : if, 

 however, the solutions be mixed together in the boiling state, 

 no precipitation takes place. Ferro-cyanate and sulpho- 

 cyanate of iron produce no change in this liquid. Sulphu- 

 retted hydrogen precipitates sulphuret of iron. 



Caustic soda and carbonate of soda decompose this solution, 

 as well as those containing less than one and a half propor- 

 tional of the silicate, after some time : when the liquid is heated, 

 decomposition takes place instantaneously. Ammonia reacts in 

 a similar way. Silicate of soda added in excess produces no 

 decomposition. A mixture of perchloride of iron and silicate 

 of soda, slowly evaporated to dryness, leaves a red-brown mass 

 of a vitreous fracture, and transparent at the edges. 



Water being poured upon the mass, it splits into fragments 

 with a crackling noise, and the water dissolves chloride of sodium 

 and perchloride of iron, or silicate of soda, if either has beea 

 added in excess. 



The washed silicate of iron yields a light brown-yellow 

 powder ; being boiled with muriatic acid, the silica is com- 

 pletely separated. 



In a solution of proto-chloride of iron, containing -—ih. of 

 the chloride, the silicate of soda produces instantly a greyish- 

 green precipitate ; and the limit where a change of colour is 

 still perceptible, is arrived at when the solution contains ^^th of 

 the chloride, whilst the caustic soda still causes a very sensible 

 cluuige of colour in a solution containing ^^ih of the chloride, 

 when the diameter of the liquid is equal to | inch. Persulphate 

 of iron being mixed with a diluted solution of silicate of soda 

 (containing ^^j^th of silica), the former being in excess, no pre- 

 cipitation of silica is produced ; but the mixture becomes de- 

 composed by boiling. With excess of silicate the mixture 

 congeals after standing twenty-four hours. 



In a solution of perchloride of mercury, which was copiously 

 precipitated by caustic soda, the silicate did not produce any 



