406 abstracts: metallography 



flutings were discovered, the most striking beginning at 0.760 /^ nearly- 

 coincident with A, and running toward the red. Circumstances indi- 

 cated that this band might be due to titanium oxide, and experiments 

 since made at the Bureau of Standards have shown a band in this posi- 

 tion in the spectrum of the titanium arc. The general conclusions ar- 

 rived at are as follows: 



1. Many stellar spectra possess sufficient intensity in the region of 

 wave length 0.80 ^ to enable this portion of the spectrum to be photo- 

 graphed on plates sensitized with dicyanin. 



2. In favorable instances stellar spectra can be well observed to 

 wave length 0.85 m- 



3. The region of greater wave length than 0.70 /x contains features of 

 importance, especially in the case of the later spectral types. 



P. W. M. 



METALLOGRAFBY.—Tijpical cases of the deterioration of Mimtz 

 metal {GO-Ifi brass) by selective corrosion. H. S. Rawdon. Bur. 

 Stand. Tech. Paper No. 103. 28 pp. December 15, 1917. 



Brass of the type 60-copper and 40-zinc, which is used commercially 

 in a variety of forms, e.g., wrought bolts, sheathing, condenser tubes, 

 extruded forms, etc., often shows a kind of deterioration by which the 

 metal changes its color to copper-red and becomes very weak and 

 brittle although the shape and size apparently remain unchanged. 

 This change of properties is due to a selective corrosion of the alloy, 

 which has a duplex structure, when exposed to the action of some 

 electrolyte, particularly sea-water. The present study includes bolts, 

 boat sheathing, condenser tubes, .and parts which were corroded while 

 under stress. 



The examination of the microstructure shows clearly the method of 

 the attack, the zinc-rich constituent being electrolytically "leached 

 out" leaving a skeleton of weak pulverulent copper. Later the second 

 constituent may be attacked so that the whole specimen is converted 

 into pulverulent "copper" — the sample becoming so weak that it can 

 be broken into fragments in the fingers. 



Conditions that appear to accelerate corrosive attack of this type 

 are : the microstructural composition of the alloy, contact with strongly 

 electronegative metals, the effect of certain adhering deposits of basic 

 zinc chloride resulting from the corrosion, the thoroughness of the 

 later than common. There was a roost of about 500 Sturnus vulgaris 



