M. TECHNOLOGY. 525 



tion. This upper layer can easily be removed by means of 

 a pipette, and the fuchsine verified by its decoloration with 

 hydrochloric acid. By a process based upon this decolora- 

 tion, using a standard solution of the acid, a quantitative de- 

 termination of fuchsine may easily be made. 1 .Z?, February 

 22,1874,356. 



PREPARATION OF TRIPOLI FOR POLISHING VARNISHED 



ARTICLES. 



Very finely pulverized tripoli is passed through a hair 

 sieve, and stirred well in water with a wooden rod; the 

 water with the fine tripoli in suspension is poured into an- 

 other vessel, and allowed to stand for an hour or longer, until 

 clear, and is then poured off. The powder obtained by dry- 

 ing the sediment on paper, in the sun or stove, is employed 

 on felt or flannel for polishing varnished surfaces, with gentle 

 friction, repeating the operation if necessary, and finally wip- 

 ing with a fine cloth. 5 C, 1874, xix., 151. 



FRICTION WITHIN RIFLED GUNS. 



Professor Reynolds, of Manchester, has presented an inter- 

 esting memoir on the relative work spent, in friction, in giv- 

 ing rotation to shot from guns rifled with an increasing and 

 also with a uniform twist. lie shows that the friction be- 

 tween the studs and the grooves consumes more work with 

 an increasing: than with a uniform twist, and that in the case of 

 grooves which develop into parabolas, such as those used in 

 the Woolwich guns, the waste from this cause is double what 

 it would be if the twist were uniform. Among his conclu- 

 sions, Professor Reynolds states that when the pressure of the 

 powder is constant, the work spent in friction in the case of 

 parabolic grooves is \\ times that spent in friction with plain 

 grooves; and that this ratio becomes two when the pressure 

 diminishes rapidly as the ball moves along; and, finally, that 

 this ratio may have any value between 1^ and 2, but that it 

 can not go beyond these limits. Jour. Soc. Tel. Engineers, 

 1873,56.^ 



TREATMENT OF LUBRICATING OILS. 



According to a patent of Baird, of Glasgow, the peculiar 

 tendency of most oils and lubricants to oxidation is removed 



