4i6 abstracts: metallography 



saliva of the pellagra patients tended to be higher than that of the con- 

 trols. The total solids, ash, organic matter and mucin of the saliva 

 was greater for the pellagrins than for the controls, but bore no rela- 

 tion to the mouth symptoms. The diastatic power of the saliva of 

 pellagrins varied within the limits established by the controls. The 

 sulfocyanate content was much less marked in the saliva of pellagra 

 patients than in that of normal people. The reaction of the saliva in 

 pellagra was found to be somewhat more alkaline than that of normal 

 saliva. M. X. S. 



METALLOGRAPHY. — Constitution and metallography of aluminum 

 and its light alloys with copper and magnesium. P. D. Merica, 

 R. G. Waltenberg and J. R. Freeman, Jr. Bur. Standards 

 Sci. Paper 337. Pp. 14, pis. 8, figs. 19. 1919. 



The temperature-solubility curves of CUAI2 and of Mg4Al3 in alumi- 

 num were determined by the method of annealing and microscopic 

 examination. Aluminum dissolves about 4.2 per cent of copper as 

 CUAI2 at 525° C. and about 12.5 per cent of magnesium as Mg4Al3 at 

 450° C. The solubility of both compounds decreases with decreasing 

 temperature. At 300° C. aluminum dissolves only i per cent of copper 

 as CuAl2 and slightly less than 5.9 per cent of magnesium as Mg^Als. 



The structural identification of the various constituents, FeAls, 

 CuAl2, Mg4Al3, found in alloys with magnesium and with copper, is 

 described, and a constituent is noted in all light aluminum alloys con- 

 taining magnesium which is believed to be Mg2Si. The solubility of iron 

 as FeAls in aluminum is at all temperatures less than 0.15 per cent. 

 Small amounts of silicon up to 0.12-0.20 per cent are dissolved by 

 aluminum at the eutectic temperature but are reprecipitated upon 

 cooling, corresponding to the diminished solubility for silicon of alumi- 

 num at lower temperatures. Silicon in the usual commercial amounts is 

 probably present as a compound of iron and silicon, together with some 

 aluminum. The composition of this compound is not known but it 

 separates out with aluminum and FeAls at an invariant point at 610° C. 



R. G. W. 



