abstracts: metallurgy 445 



Hence it was decided that 30 freezings are not enough to give a trust- 

 worthy indication of the durabihty of such materials. An apparatus 

 has been installed which automatically shifts the specimens back and 

 forth between a cold chamber and warm chamber at certain intervals. 

 With the use of this apparatus, it is possible to make a great number 

 of freezings which will correspond to several years of exposure to the 

 weather. It is proposed to make extensive weathering tests with 

 this apparatus to determine more definitely the relative effect of frost 

 action on the different marbles as well as other types of building stones. 



Electrical resistivity tests were made on a number of different types 

 to determine their relative value as insulators and resistivity under 

 different conditions of moisture. The results show a considerable 

 range of values indicating that there is a choice of marble for use in 

 switch boards and allied purposes. 



Measurements of the thermal expansion made on a few samples of 

 marble in this investigation show that this material does not expand 

 at a uniform rate even at ordinary temperatures. As the tempera- 

 ture is increased the rate of expansion increases, hence it is not possi- 

 ble to state a coefficient of expansion for marble that will hold good for 

 any very great range of temperatures. Another peculiarity brought 

 out by these tests was the fact that marble when expanded by heating 

 does not contract to its original dimensions as the temperature is low- 

 ered, but retains a part of the increase permanently. A number of 

 successive heatings show the same effect, each adding an increment of 

 length to the specimen. 



A few cases of warped marble slabs are illustrated and a discussion 

 is given of the causes which may be instrumental in bringing about 

 this warping. 



METALLURGY. — Aluniinuin and its light alloys. Bur. Stand. Cir. 

 No. 76. Pp. 120. 1919. 



This circular attempts to give all available information concerning 

 the physical and mechanical properties of aluminum and its light 

 alloys in summarized form. Commercial alloys are described and 

 compared. The corrosion and disintegration of aluminum and its 

 alloys are considered. 



The endeavor has been made to reproduce only such data as have 

 passed critical scrutiny. Wherever possible, data and information have 

 been put into the form of tables and curves. A complete bibliography 

 and specifications for aluminum and its light alloys are given. 



J. F. Meyer. 



