PAINTS, DYES, AND VARNISHES 



For using any of these oils special lamps are made, 

 having different kinds of burners adapted to the various 

 oils, some of them being very much like the ordinary 

 kerosene lamp used for illumination. As a rule, how- 

 ever, a wickless burner of some kind is less expensive 

 and preferable, such lamps being arranged so that they 

 receive a continuous feed of oil, with an apparatus for 

 regulating the supply of air, and a chamber for collect- 

 ing the soot as it forms. 



The soot so formed is not pure carbon, but contains 

 varying quantities of the products of distillation. For 

 ordinary purposes, however, these impurities are not 

 sufficient in quantity to impair the quality of the pig- 

 ment. But if a perfectly pure carbon is required, it 

 may be obtained by boiling the lampblack with a solu- 

 tion of caustic soda, and then treating the residue with 

 some acid. 



A very simple apparatus for obtaining a continu- 

 ous supply of fairly good soot is one in which the flame 

 of the oil lamp is brought in contact with a revolving 

 iron cylinder, fitted with a water-chamber for keeping 

 it cool. As the flames come in contact with this cooled 

 surface the soot is deposited in a continuous line, which 

 is removed by brushes placed on the opposite side of 

 the cylinder, or at some convenient point. The soot so 

 gathered is received on an inclined plane, down which it 

 slides into the receiving-box. Such an apparatus is 

 simple and inexpensive, and by its continuous action 

 produces an enormous quantity of soot in the course of 

 the working-hours of a day. 



The peculiar black pigment known as India ink is a 

 VOL. vm. 18 [ 273 1 



