M. TECHNOLOGY. 563 



heat, and inserting them into hard sealing-wax, allowing 

 tlieni to remain but a second, then pushing them again into 

 another part of the wax, and again quickly withdrawing, to 

 repeat the operation in a fresh spot, until they are too cold 

 to penetrate the wax. The tool is to be moistened with tur- 

 pentine when used. 14 (7, 1872, ccvi., 419. 



AVHITE METAL ALLOYS FOK MACHINERY. 



An alloy of 90 per cent, of tin, 8 per cent, of antimony, and 

 2 per cent, of copper, has been found excellent for crank and 

 connectinsf-rod bearinojs on the Moscow and Nishni railroad. 



CD Cj 



On the Kursk-Charcow-Asow railroad an alloy of 78.5 j)er 

 cent, of tin, 11.5 per cent, of antimony, and 10 per cent, of 

 copper has been found very superior for pivots of all kinds, 

 slide-valves, eccentrics, stuffing-boxes, etc. The Swiss Nor- 

 dostbahn Company, in ordering locomotives recently, requir- 

 ed the following preparation as a composition for axle-jour- 

 nals: 10 parts of antimony added to 10 parts of melted cop- 

 per, with 80 parts of tin added, and the alloy run into bars, 

 to be rcmelted for. use. 6 (7, November 21, 18Y2, 468. 



PURIFICATION OF CAUSTIC SODA. 



The sulphur compounds present in caustic soda, prepared 

 by lime on a commercial scale, are entirely removed by the 

 simple and effective process of Helbig, of Gera, who uses a 

 blast of air, instead of simply converting them into less ob- 

 jectionable sulphate of soda by the employment of saltpeter. 

 The lye is evaporated as usual in iron kettles. When a cer- 

 tain degree of concentration is reached, the cyanogen com- 

 pounds are decomposed, with effervescence and development 

 of ammonia, as well as the separation of graphite. The scum 

 then settles, and the mass becomes semi-fluid. The heat is 

 increased until the mass is red-hot and liquid ; air is then 

 forced in through an iron tube passing through the cover and 

 reaching to the bottom, with such violence as to keep the 

 mass in agitation, and is continued until most or all of the 

 sulphur is oxidized. Portions are withdrawn and examined 

 during the operation. After settling, the caustic soda is re- 

 moved as. usual. The graphite that settles during the opera- 

 tion floats on the top, and may be removed; but since it is 

 useless for pencils, paint, etc., it is generally allowed to con- 

 sume. 14 C, 1872, ccvL, 375. 



