342 abstracts: technology 



are due to laminae of smaller index and of thickness of the order of a 

 hundredth of a millimeter. They do not seriously affect the optical 

 qualities of lenses or prisms. The second class of striae in general does 

 not affect the optical performance ; but, in the case of lenses and 

 plane parallel plates, etc., in which the light traverses the striae at 

 approximately normal incidence, the performance may be quite as good 

 as with a perfect specimen. A. A. M. 



TECHNOLOGY. — The table of unit displacement oj commodities. 

 Bur. Stand. Circ. No. 77. Pp. 67. 1919. 



This circular showing (i) the number of pounds per cubic foot as 

 packed for shipment, (2) the number of cubic feet of space required for a 

 short ton, (3) the number of cubic feet of space required for a long ton, 

 and (4) the manner in which the material is packed, lists several hundred 

 commercial commodities alphabetically. Appendixes give special 

 information concerning automobiles, canned fruits and vegetables, and 

 fresh fruits and vegetables. 



This table has been prepared to meet an immediate demand for such 

 information and will be revised and augmented from time to time as 

 further data are obtained. The Bureau will, therefore, be pleased to 

 receive information, criticisms, and suggestions from those interested 

 in the table. H. M. RoESKR. 



TECHNOLOGY.— 5o/(f^r5 for aluminum. Bur. Stand. Circ. No. 

 78. Pp. 9, pis. 2. 1919. 

 The use, serviceability, method of application, and composition of 

 solders for aluminum are discussed in the light of special tests made 

 at the Bureau of Standards on commercial and other compositions of 

 solders. All soldered joints are subject to rapid corrosion and disinte- 

 gration and are not recommended except where protection from cor- 

 rosion is provided. Suitable compositions for solders are obtained 

 by the use of tin with the addition of zinc or both zinc and aluminum 

 within wide percentage Umits. Solders are best applied without a 

 jBlux. The higher the temperature at which the "tinning" is done, 

 the better the adhesion of the tinned layer. A perfect union between 

 solder and aluminum is very difficult to obtain, but the joint between 

 previously tinned surfaces may be made by ordinary methods and with 

 ordinary soft solder. Only the tinning mixture need be special. Tables 

 of the composition of many solders are given. J. F. M^yer. 



