272 REPOET — 1889. 



maximum tensile strength in the material made by Mr. T. Turner, and 

 later by Mr. Keep, in their numerous tests as to the effect of silicon 

 upon cast-iron. The diagram referred to, and given above (Diagram 1), 

 shows that by a diminution in the silicon highly graphitic pig-iron 

 becomes rapidly mottled, and eventually white, although, practically, 

 none or but little total carbon is oxidised, and this, as far as can be seen, 

 solely by the fall of the silicon from 2-50 to 1'70 per cent. Whilst, 

 therefore, Messrs. Turner and Keep show that white iron can be con- 

 verted into mottled, and eventually grey, by means of additions of silicon, 

 this diagram shows the converse, namely, that with silicon abstracted 

 grey cast-iron becomes mottled and eventually white. 



Outside, one might say even within, the laboratory, the properties of 

 the metalloid silicon, or silicium, are but little known. No fuller details 

 can be found than in that part of Dr. Percy's work ' Metallurgy ' relating 

 to silicon where all the methods for its production on a laboratory scale 

 are given. 



It is ordinarily described as a non-metal, very hard, dark brown in 

 colour, a non-conductor of electricity, lustrous, not readily oxidised, and 

 soluble in all ordinary acids with the exception of hydro-fluoric. It is 

 said to resemble carbon in its general properties. Others add that it exists, 

 like cai'bon, in a graphitic, amorphous, and combined or adamantine form ; 

 but this is still to be determined. 



Mr. Henry J. "Williams, St. Louis, Missouri (U.S.A.), this year pre- 

 sented a paper to the American Institute of Mining Engineers on ' The 

 Determination of Silicon in Ferro-Silicons : its Occurrence in Aluminium as 

 Oraphitoidal Silicon, and a Study of its Reactions with Alkaline Carbon- 

 ates.' As the latest investigation of this kind, it may be well to refer to 

 the experiments. Mr. Williams's method of determining the metalloid 

 was by means of fusion with sodium carbonate, the idea being to dissolve 

 it as soluble sodium silicate, and leave the iron in a very spongy and finally 

 divided condition so as to he readily attacked by acids. He noticed some 

 curious facts during fusion. As soon as the sodium carbonate was 

 thoroughly melted and the heat reached its maximum, the reaction be- 

 came very violent, bubbles of gas (carbonic acid) rising to the surface 

 and bursting into flame. This had been noticed before by another 

 observer making experiments of similar nature with graphitic pig-iron. 

 Mr. Williams was, however, somewhat puzzled, as the ferro-silicon with 

 which he was experimenting was high in sihcon and comparatively very 

 low in carbon ; yet it gave the same result. To ascertain why silicon 

 acts exactly like carbon during the reduction, he endeavoured to obtain 

 an iron entirely free from foreign elements, particularly carbon, but con- 

 taining high silicon, but was unsuccessful. He found the desired condi- 

 tion realised in the aluminium of trade, most of which, in spite of its name, 

 he states, contains not less than 3 per cent, or 4 per cent, of silicon, but of 

 course no carbon. He found that a large part of the silicon in such alumi- 

 nium seemed invariably present as an allotropic modification of that metal- 

 loid, crystallising in fine glistening black plates resembling some forms of 

 graphite, and considered that this was evidently the graphitoidal form 

 of silicon which Deville has mentioned in connection with aluminium, 

 but which has not yet been isolated or found to exist in ii-on. Dr. Percy 

 mentioned at length the same fact, and describes the material as resem- 

 bling graphite from iron smelting-furnaces, and as being hard enough to 

 scratch glass, with a specific gravity of 2-49. As regards, however, the 



