1903.] The Properties of the Aluminium-Tin Alloys. 277 



" The Properties of the Aluminium-Tin Alloys." By W. CARRICK 

 ANDERSON, M.A., D.Sc., and GEORGE LEAN, B.Sc. Communi- 

 cated by Professor H. A. MIERS, F.RS. Keceived June 16, 

 Kead June 18, 1903. Eeceived in revised form August 8, 

 1903. 



[PLATE 15.] 



Aluminium and tin may be melted together in all proportions to 

 give uniform fluid mixtures. The melting cannot be done in the 

 ordinary fireclay or plumbago crucibles, since the admixture of tin 

 appears to increase greatly the power which aluminium has to reduce 

 the silicates of fireclay, the reduced silicon becoming absorbed in the 

 body of the metal. In our earlier experiments on these alloys we 

 learned that, even with careful melting at a temperature not higher 

 than about 750 C., it was impossible to prevent this rapid reduction 

 of silicon. In a few minutes the alloys became badly contaminated 

 with the metalloid; in one instance as much as 11 per cent., partly 

 crystalline and partly amorphous, was found in the cooled ingot. On 

 this account the metal was in our subsequent experiments invariably 

 melted in small crucibles of baked carbon. These were packed by 

 means of asbestos inside fireclay crucibles of the ordinary Battersea 

 type. The ingots made in this way were found to be uncontaminated, 

 and contained only traces of silicon and iron from the aluminium 

 employed, which was the best quality Foyers product. The weight of 

 metal used in each experiment was from 10 to 40 grammes. 



Cooling Curve. 



In a preliminary paper on the nature of these alloys, read before 

 the British Association at its Glasgow Meeting in 1901,* we 

 showed that above the eutectic limit the cooling curve of each 

 alloy always reveals two breaks. The general form of the curve 

 is as we then stated it to be. It has the usual extended form 

 corresponding to the gradual separation of mixed crystals from the 

 solution during cooling, and the first break point is continuously 

 lowered with every increment of tin. The second break, which marks 

 the solidifying point of the eutectic, we were at first inclined to place 

 at 232, or very little below that temperature. More careful working, 

 however, with a larger number of alloys, has enabled us now to place 

 it nearer the figure originally stated by Hey cock and Neville,! and 

 rather under it, viz., 228 228 -5. 



* ' B. A. Kep.,' 1901, p. 606. 



f ' Journ. Ckem. Soc.,' 1890, p. 376. 



