540 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



in great excess, is added to caoutchouc softened in bisul- 

 ]3hide of carbon, it effects the change called vulcanization at 

 ordinary temperature, or upon slight warming. When the 

 mixture contains an excess of the chloride of lime, the mass 

 does not become pasty, but remains pulverulent. Scientific 

 American, XXXIL, 374. 



CAUSTIC SODA AND POTASH. 



Griineberg & Vorster have patented in England a new 

 process for obtaining the caustic alkalies. The chloride of 

 sodium or of potassium, as the case may be, is mixed with 

 hydrated alumina, and the mixture subjected to the action 

 of suj:>erheated steam. 14 C, February, 382. 



GLASS MANUFACTUEED FEOM SULPHATE OF SODA, OE CAL- 

 CINED GLASS. 



Dr. Guhrauer calls attention to the fact that, although 

 sulphate of soda can not as yet be employed in the manu- 

 facture of a colorless glass suitable for glass vessels, it is ex- 

 tensively used in France, Belgium, and Holland to furnish 

 the alkali in the manufacture of mirror-glass, although it has 

 too decided a tint when even less than an inch in thickness 

 to be used for half-crystal ware, etc. The process by which 

 a glass suitable for the special purpose mentioned is made 

 from sand, lime, sulphate of soda, and charcoal alone, rests 

 upon the previous calcination of the glass mass, or the prep- 

 aration of what may be called a finely divided, calcined 

 glass ; this is accomplished by allowing the barely fused 

 mass to flow suddenly into cold water. After thoroughly 

 drying this it is again fused, with the addition of broken 

 glass, decolorizing and purifying material, as binoxide of 

 manganese, nitre, etc. ; but the desired degree of freedom 

 from color depends in a great measure on the careful selec- 

 tion of the raw material, and the proportions in which the 

 ingredients are mixed. Any furnace, upon any system of 

 heating, will answer, and the glass, when in a very viscid 

 condition, may be simply run oft* through openings, closed 

 by valves through which water circulates, into tanks filled 

 with water, from which it is then taken and dried, and 

 re-fused. The consumption of time and fuel, by reason of 

 the double fusion required, is not necessarily much, if indeed 



