764 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



Coal-tar Products. 

 M. Boboeuf, a French chemist, has treated coal-tar with soda, at 

 the ordinary temperature, and obtained benzol, the material "vrhich 

 is the starting point in the manufacture of aniline dyes. The soda 

 is said to combine with the heavy constituents of coal-tar ; the 

 benzol which floats on the surface of the solution is easily separa- 

 ted by decantation, and is found to be contaminated only with 

 products lighter than itself, which are carried off by a single dis- 

 tillation. The soda compound is chiefly the carbolate of soda 

 (phcnate of soda), which possesses all the valuable disinfecting 

 properties of phenic acid. 



A New Battery. 

 M. Rourillion has described, before the French Academj'-, a new 

 arrano"ement for generating an electric current hy the action of 

 aqua regia. A mixture consisting of two-thirds hydrochloric acid, 

 one-third nitric acid, or three-fifths hydrochloric and two-fifths 

 nitric, will easily dissolve gold and platinum, but will only super- 

 fi.cially attack pure unalloyed silver ; a superficial ehloride being 

 formed which protects the rest of the silver like an impermeable 

 varnish, however long it may remain in the aqua regia. If copper 

 be present the metal is attacked. Rouillion has utilized this fact 

 by making a battery in which pure silver in aqua regia replaces 

 carbon of the Bunsen cell, or platinum of the Grove, in nitric acid. 

 After using the battery for several months he found no diminution 

 in the quantity of silver and no chloride of silver was formed in 

 the porous cell. The inventor states that his battery is more con- 

 stant than Bunsen's. It further tests confirm this statement the 

 new battery will soon be brought into practical use. 



Caoutchouc Septa. 

 Mr. Thomas Graham, the distinguished chemist, in a remarkable 

 memorial to the Royal Society, " On the Absorption and Dialytic 

 Separation of Gases by Colloid Septa," states that a thin film of 

 India-rubl)er is impervious to gases, but that the gases may become 

 liquified by contact with such septa, and then transmitted through 

 it by the agency of liquid, and not gaseous diffusion. M. Payen, 

 of France, has taken exception to this statement. He declares 

 that India-rubber abounds with pores through which a gas could 

 pass while in the gaseous condition ; under the microscope they 

 are visi))lc when the ruljbcr is dry, l)ut arc greatl}' enlarged, and 



