310 C1IEMISTET. 



appearance (visible in the dark) at the point where they enter the cooled part of 

 'the tube. This luminosity may be observed even when the mixture has been ex- 

 posed to the air for a long time, one part in one hundred thousand of Bour can be 

 readily detected. The liquid which condenses c< iall globules of phos- 



phorus ; one-third of a grain was detected thus in five ounces of material. When 

 much phosphorus is present, phosphorous and phosphoric acids may ba detected in 

 the distillate, which is not the case if the acids themselves are subjected to distilla- 

 tion with sulphuric acid. 



SILICA. 



Ludwig has shown that hydrated silica, precipitated from its solution in potash 

 by chloride of ammonium, obstinately retains traces of ammonia and potash, and is 

 soluble in 10,000 parts of water. Also that by treatment of the silicate of potash 

 with hydrochloric acid in excess, the whole of the alkali cannot be removed, but a 

 portion remains, probably as an acid silicate. This even after calcination is some- 

 what soluble in water, in the proportion of of silica to 2J ' ts of 

 water. 



SILICIUM. 



Wohler prepares silicium by fusing aluminum with an excess of the double fluoride 

 of silicium and potassium in an ordinary crucible at a heat about that required for the 

 fusion of silver. On breaking there is found in the midst of the fused salt a very 

 brittle ingot of crystalline texture and dark iron colour. This appears to be the 

 compound of silicium and aluminum observed by Deville, containing in this case a 

 very large quantity of silicium in the stale of graphite. According to the length of 

 fusion it contains from 75 to 80 of silicium, which, is easily obtained by treating the 

 ingot with hydrochloric acid. 



Deville has obtained silicium in measurable crystals by passing the vapour of 

 chloride of silicium over aluminum heated to bright redness; the crystals thus 

 formed are treated successively with nitro-hydrochloric acid, boiling hydrochloric 

 acid, and fused bisulphate of soda. "When the operation is not complete, siliciuret 

 of aluminum is formed, containing 40 to 50 per cent, of silicium. In this operation 

 the silicium being separated from the chloride is dissolved in the aluminum forming 

 a solution, which when saturated allows the silicium to It appears that 



boron may be obtained in the same '-ut is very difficult to purify. 



Carbo i, not being soluble in aluminum, can ned in this way, but if pig 



iron be employed instead of aluminum «■ is obtained in a form diri i 



from graphite. 



If fluoride of silicium be cm. eautiful crystals of fluor- 



ide of aluminum are oM&ined, ; cti resemblance to fluor spar. They 



are not acted upon by sulphuric, hydrofluoric or nitrofluoric acids; the same 

 crystals can be obtained by treating calcined alumina with excess of hydrofluoric 

 &C ] L \ | . tube of platinum in a current of hydrogen. 



or COBALT. 



A. Btromeyer finds that the yellow salt obtained by Fisher on mixing a salt of 

 cobalt with nitrite of potash, has not the formula given by St. Evre but the follow- 

 ing: Co 2 O 3 , 2N'O s + aKO NO 8 + 2110. Its formation may be employed as a test 

 for cobalt if not more than 300 p I er be present to 1 part of Co 0. 



A triple salt is formed when lend is present. Stromeyer forms the nitrite of 

 potash by fusing 10! a pan and >dding 208 parts of lead, con- 



