L. TECHNOLOGY. 493 



joint action of heat and vacuum, any excess of that acid, 

 which, however, not only saturates free alkalies and carbon- 

 ate of lime, but also sets the organic acids which may be pres- 

 ent, as alkaline salts, free from those combinations. The sul- 

 phurous acid thus takes hold of the bases they were combined 

 with, while the greater part of the organic acids are volatil- 

 ized along with the steam. Thus the sulphurous acid pro- 

 motes the good and ready crystallization of the sugar, while 

 its action as a decolorizer comes also into play. The details 

 of the new process embrace the two operations of the manu- 

 facture of the acid in a simple form, and its introduction into 

 the vacuum pans. The quantity to be applied in any solution 

 varies from four to eight, or from ten to fifteen per cent, of 

 the bulk of liquid sirup to be evaporated. The process is said 

 to involve very little cost, to require no inconveniently large 

 space, to be applicable to any existing manufactory, and to 

 be very easily understood by manufacturers. 1 A, November 

 18,1870,248. 



PEEFOEATING MACHINEEY. 



At the present time the machinery first brought into play 

 for perforating sheets of postage stamps, in order to their 

 more ready separation, is now applied to many other pur- 

 poses, especially- for coupons, bank checks, and other similar 

 objects, by which the necessity of using a pair of shears is 

 avoided. We hear of a new instrument, made in Germany, 

 intended for such purposes, Avhich is reported to be very com- 

 plete, and to be furnished at a moderate price. It is said to 

 weigh about two hundred pounds, and is thirty inches in 

 length and in breadth. 9 C, September, 1870, 67. 



FACILITATING THE DRYING OF PEINTEES' INK. 



The addition of one per cent, of borate of manganese to 

 printers' ink will, it is said, cause it to dry much more rapid- 

 ly than usual. 13 C, March 15, 1870, 429. 



PRINTING ON TIN. 







A method of printing on tin is now used very largely for 

 labeling boxes and other vessels, so as to avoid the necessity 

 of affixing paper labels, which are so liable to come off. The 

 colors adhere with such tenacity that the tin may be wrought 



