98 ANNUAL OF SCIENTIFIC DISCOVERY, 



and unwholesome-looting black sugar into a fine -white sugar is com- 

 pleted in one-seventh of a second by this process. The principle 

 adopted is precisely that employed in "gassing" lace --an operation 

 resorted to for the purpose of removing the minute filaments of cotton 

 adhering to the surface of the fabric. In the case of the crystals of 

 sugar, a thin film of fluid matter is required to be removed from the 

 surface of the crystal, and this is effected by bringing it in contact 

 with water a material which would as quickly dissolve the crystal 

 itself, as the flame of the gas would destroy the delicate and fragile 

 web of the bobbin net. How can the water be thus brought into 

 contact with the sugar for such a short period, and in such a manner 

 as only to remove the outer coating of molasses, and leave the crystal 

 uninjured ? The process is a very simple one. A table of nine feet 

 in circumference is made to revolve eight times per minute, having a 

 coating of sugar spread over it to the depth of half an inch, and 

 which consequently moves over a space of 72 feet per minute. At 

 one part of its revolution the table is made to pass under a pipe of 

 two inches in diameter, from which a shower of water is falling, and 

 as the pipe is but one-sixth of a foot in diameter, and the table passes 

 it at the rate of 72 feet per minute, it follows that each portion which 

 comes under the falling water will be retained only 1-432 of a minute 

 in each revolution. This table being covered with thin brass wire 

 gauze, has placed immediately under it a vacuum chamber, into which 

 the falling water, carrying with it the semi-fluid coating of molasses, 

 is drawn as the table revolves, the crystallized sugar remains on the 

 surface pure and white, and is delivered by a scraper into the hogs- 

 head placed for its reception. 



IMPROVEMENTS IX THE MANUFACTURE OF ROSIN OIL. 



BY an improved process patented by Mr. Thuck, of England, the 

 acid, naphtha, and oil, are produced successively from the rosin as 

 follows : 



A still is filled to about two-thirds its contents with rosin, amongst 

 which, by means of a pipe fitted with a perforated coil near the bot- 

 tom of the still, a jet of steam is introduced at or before the time of 

 lighting the fire. As in the first stage of heating, the rosin is very 

 apt to boil over, the still must be disconnected from the condenser to 

 avoid the injury and explosion that might ensue, were the boiling 

 rosin to enter the condenser. The heat must be gradually increased 

 till it reaches 325 Fahr., when acid will be discharged, and the 

 temperature must not be kept stationary till the acid ceases to flow. 

 During the whole of the distillation, steam is injected by the pipe 

 above mentioned ; it passes through the rosin, and carries off' the 

 naptha with it in the form of vapor. The quantity of naphtha so 

 produced is about 15 per cent, of the bulk of the rosin under 

 treatment. 



The acid and naphtha being run off, the temperature is raised to 

 550 Fahr., and oil passes otf as vapor, and is condensed, being in 



