228 ' ANNUAL OF SCIENTIFIC DISCOVERT. 



the copper solution, with 1 part sulphate of copper, 16 parts of 

 water, ammonia suflSeient to redissolve the precipitate formed 

 when it is added. Zinc and gah^anized iron can be treated, ac- 

 cording to Boetger, directly by the copper solution, without using 

 the tin salt. 



Action of Water of Lead. — Professor Boetger, inquiring into the 

 cause of the action of distilled water on lead, has found it to be due 

 to the presence of carbonate of ammonia, and not, as is usually 

 ascribed, to the air dissolved in the water. After having been 

 boiled for a time, distilled water will not attack the lead until after 

 a considerable exposure, when a reabsorption of ammonia and 

 carbonic acid from the air, where they are always present, may 

 be supposed to have taken place. Boetger has further found that 

 the alloying of the lead with a small amount of tin protects the 

 former from being acted upon, and this fact suggests the advan- 

 tage of purposely introducing a little tin into the metal from which 

 lead piping is to be manufactured. 



Combustion. — The perfect combustion of 1 ton of anthracite 

 coal, or of coke, requires over 5,970 pounds of oxygen, derived 

 from about 340,000 cubic feet of air at ordinary temperature, 

 equivalent to a column 1 foot square and over 64 miles in length. 

 This calculation is based upon the supposition that all of the oxy- 

 gen of the air is made available ; but in practice it is found neces- 

 sary to introduce twice the quantity of air that by calculation 

 would be suflScient. 



In the conversion of 1 part of solid carbon into carbonic oxide, 

 there are involved 2,473 heat units. In the conversion of the car- 

 bonic oxide thus obtained into carbonic acid, there are involved 

 5,607 heat units, making 8,080 heat units in all, of which the first 

 or imperfect combustion yielded but 31 per cent, of the obtainable 

 heat ; so that to limit the supply of air, so as to cause the exclusive 

 production of carbonic oxide, would necessitate the use of three 

 times as much fuel as would be required to do the same work 

 were it properly burned. 



GaliherVs Apparatus Improved. — This patent hood, by means of 

 which any person can penetrate into poisonous atmospheres with- 

 out danger, has been described in "Annual of Scientific Discov- 

 ery " for 1868, pp. 83, 84. While communication is kept up with 

 the external atmosphere, the wearer of the apparatus is obliged to 

 rebreathe the air expired by his lungs, and the latter soon becomes 

 surcharged with carbonic acid. M. Galibert now obviates this 

 difficulty by providing a receiver, into which he puts potash, the 

 efi'ect being to absorb the poisonous gas and make the expired air 

 again fit for respiration. 



Preparation of Oxygen and Chlorine. — In a paper communicated 

 to the Academy of Science, M. A. Mallet stated that between 200® 

 and 400° F., and in presence of steam, protochloride of copper 

 absorbs oxygen from the air almost instantaneously to form an 

 oxychloride, which parts Avith its one atom of chlorine at a higher 

 temperature. So that oxj^gen gas, or chlorine gas, can be pre- 

 pared at will, and in as large proportions as we wish, the same 

 protochloride of copper serving over and over again. 



