j^n Attempt to analyse Silica. 805 



pulverized sufficiently fine, owing probably to the slow cool- 

 ing of the crucible. I therefore mixed it with clean pow- 

 der of flints, and attempted by means of a new fusion to get 

 it malleable with an increased charge of silica, when the 

 carbon of the cast iron should have reduced the earth. The 

 lilicated iron obtained was soft, but intermixed with more 

 or less malleable iron, as in the preceding experiments. 



g. 4*3 grammes of silicated iron from that so prepared, 

 being well cleansed, were dissolved in diluted muriatic acid 

 by means of such apparatus as was used in the preceding 

 experiments. The solution was boiled towards the con- 

 clusion, for the purpose of expelling all gas out the vessel, 

 which, together with the atmospheric air out of the appa- 

 ratus, made 77 decimal cubic inches. This amounted to 

 near three cubic inches more than what an equal weight of 

 bar-iron had produced, when dissolved in muriatic acid in 

 the same apparatus. This indicates that the silicated iron 

 did contain a body which absorbed more oxygen than pure 

 iron, and so much the more, as the great charge of carbon 

 would have presupposed a less quantity of disengaged gas. 

 The gas on burning over lime water left 03075 gr. car- 

 bonate of lime, answering to 0'134 of carbonic acid, or 

 0-038 1 of carbon (0"846 per cent, of the weight of the iron, 

 nearly as much as in the preceding experiment). The acid 

 left undissolved a dark siliceous earth, which after drying 

 was of a light gray colour, and weighed 0*578 gr. During 

 ignition in a closed vessel, it disengaged a gas of an em- 

 pyreumatic smell, which in combustion burnt with a blue 

 flame. By this ignition the earth lost O'OIS of a gramme, 

 but did not become while. Carbon was found in that which 

 was expelled, and I think I cannot be much mistaken if I 

 Kt it down at 0005 gr. The grayish siliceous earth, when 

 ignited for half an hour in a half covered platina crucible, 

 Suffered no diminution of weight, but did not acquire a full 

 whiteness. The solution of iron, oxidated with nitric acid, 

 was precipitated with caustic ammonia, and yielded 6*0 

 granuncs of red oxide. Dissolved in muriatic acid, it left 

 O'Olj of a gramme of silica; and from the water employed 

 in washing was obtained, after evaporation and the i^rnition 

 of the salt, 0007 5 of a gramme more of the same earth ; so 

 that the whole quantity of silcx became ()"5875 of a grannne. 

 If from 6 grammes of red oxide of iron 0'015 of a gramme of 

 Biliceoiis earth bedcducted, there will rcmain5-9S5 grammes, 

 corresponding to 4* 15 grannncs ot pure iron, which being 

 addtJ to 0-0431 o\ carbon, make 4" I j)3 1 grammes. These 

 deducted from 4-5 grammes, there remain 0'30G9 for base 



of 



