CHEMICAL SCIENCE. 179 



while the other component element of the carbon is given forth, and so 

 produces in its escape the blisters in question. On this assumption we 

 come to a very interesting question What is the nature of this gas ? 

 In order to examine this, all that is requisite is to fill a wrought-iron 

 retort with, a mixture of pure carbon and iron filings, subject it to a 

 long-continued red heat, and receive the evolved gas over mercury. 

 Having obtained the gas in question, in this manner, then permit a 

 piece of polished steel to come in contact with this gas, and, in all 

 probability, we shall then have reproduced on the surface of the steel 

 a coat of carbon, resulting from the reunion of its two elements ; viz., 

 that of the metallic base of the carbon then existing in the steel, Avith 

 the, as yet, unknown gas : thus synthetically, as well as by analytic 

 process, eliminating the true nature of steel, and that of the elements 

 or components of carbon." 



COATING IRON WITH ZINC AND OTHER METALS. 



MESSRS. Gressel and Redwood, of London, have recently patented the 

 following methods of coating iron with zinc and other metals. To 

 coat iron with zinc. The zinc is melted in an open vessel, and on its 

 surface is placed a layer of the chloride of zinc, or a mixture of equal 

 parts of chloride of zinc and chloride of potassium, in the proportion of 

 eight of the former to two of the latter. When the salt is in a state 

 of fusion, the metal to be coated is placed in the bath, and allowed to 

 remain there till a coating of sufficient thickness has been obtained ; it 

 is then withdrawn, and any parts of its surface imperfectly covered are 

 sprinkled with sal-ammoniac, and the sheet of iron again immersed in 

 the bath. To coat iron with tin. The tin is first melted, with a stra- 

 tum of chloride of zinc and sal-ammoniac on its surface, and the iron or 

 metal to be coated is immersed in the molten metal until sufficiently 

 covered. To coat iron with silver. The metal must be first amalga- 

 mated with mercury by the following process : 12 parts of mercury, 

 1 of zinc, 2 of sulphate of iron, 2 of muriatic acid, and 12 of water are 

 mixed together, and heated in an open vessel to about 20CH Fahr. ; the 

 iron is then immersed, and the mercury rubbed in its surfaces until 

 amalgamation is effected. The silver or alloy is to be melted in a cru- 

 cible, and the amalgamated iron placed therein, when a coating of 

 silver or alloy will be deposited. To coat iron with copper or brass. 

 The copper or other coating is to be melted in a suitable vessel, and a 

 stratum of borosilicate of lead placed on its surface ; the iron is then to 

 l)e plunged into the molten metal, and retained there until a coat- 

 ing is deposited on it. Iron coated with tin or lead may be treated in 

 a similar manner. Another method of coating iron with copper is to 

 place in a crucible a quantity of chloride of copper, upon which is laid 

 the iron to be coated, and over that a quantity of charcoal. The cru- 

 cible is then submitted to a red heat, and the chloride of copper fused, 

 and a coating of copper deposited on the iron. Or the vapor of chlo- 

 ride of copper may be employed for the same purpose. The coating of 

 copper, thus obtained, may be converted to one of brass by exposing 

 the sheet of metal to the vapor of zinc in a closed vessel. 



