M. TECHNOLOGY. 545 



amount of silicic acid will be retained, in a manner analo- 

 gous to alumina in dyeing. 14 C, CCXIII., 528. 



SOLDERING PLATINIZED GLASS SURFACES TO METALS. 



It has been found by Dr. Ronzgen that glass can be more 

 firmly affixed to metals by coating it with platinum, and 

 soldering, than it can be by cement. The tinning of the 

 platinum surface is very easily effected by means of a sol- 

 dering iron and chloride of zinc. The excess of platinum 

 coating may be wiped off with filter-paper dipped in dilute 

 hydrofluoric acid. The glass, of course, should be carefully 

 warmed before apj^lying the soldering-iron. The platinum 

 coating is said to adhere to the glass so firmly that a well- 

 soldered piece of metal can not be removed without injuring 

 the surface of the glass. 5 (7, XXXIIL, 1874, 264. 



IMPROVED MODE OF CLOSING BARREL HOOPS. 



It is claimed that the ends of hoops on barrels may be 

 securely joined with great economy of time and labor on the 

 following plan, devised by Cattin : A small plate of sheet- 

 metal has two slits punched in it in such a way that the 

 hoops may be drawn through them readily in one direction, 

 and are prevented from slipping out by the sharp edges of 

 the plate cutting into them. The surface is rendered smooth 

 by a blow with a hammer on the projecting ends of the 

 hoops. 9 C, July, 1874, 105. 



UTILIZATION OF LEATHER WASTE. 



While numerous processes for utilizing the offal in the 

 manufacture of leather are in successful operation, there has 

 been a comparatively open field respecting leather waste. 

 At the Vienna Exhibition, leather was shown suitable for 

 heels, toe-caps, and inner soles, prepared from leather clip- 

 pings, according to a French method, by simply mixing 

 them with some adhesive substance, forming the mass into 

 rectangular plates on top of each other, subjecting them to 

 hydraulic pressure, and then drying and rolling them. This 

 article was restricted in use because it could not withstand 

 moisture. A Copenhagen firm, how T ever, exhibited, for the 

 first time, an article made upon an entirely different plan. 

 The leather scraps were first converted, in a suitable ma- 



