498 



METALS. 



tion of the formation of oxysulphurets of lead, 

 antimony, and copper ; also the complete dis- 

 solution in the lead of the silver and gold con- 

 tained in the basic silicates, free from sulphur, 

 without the antimony or copper being able to 

 dissolve in the lead, and consequently to in- 

 jure it; also the obtaining, as the result of a 

 series of liquations, of a cupellable lead rich 

 in precious metals; and, finally, a consider- 

 able saving in the net cost of the industrial 

 extraction of gold and silver by means of the 

 cupola. 



Zinc Sheathing. Experiments have been 

 made by the British Admiralty to test the effi- 

 ciency of covering iron plates (for ships) with 

 zinc. These have proved satisfactory, espe- 

 cially where no insulating medium had been 

 placed between the two metals, a result which 

 might have been expected, as, owing to the 

 electric relations between iron and zinc, the 

 former is preserved, by contact with the latter, 

 from sea-water corrosion. In a paper read 

 before the Civil and Mechanical Engineers' 

 Society, Mr. W. F. Black described Mr. Daft's 

 proposed method of building ships with a spe- 

 cial view of providing a simple means for the 

 attachment of zinc sheathing. That gentle- 

 man proposes to rivet all the plates of the ves- 

 sel directly to the frames or ribs, and that the 

 joints shall be made on the lap principle 

 throughout, but in such a way that a flush 

 surface shall be obtained. This he effects by 

 leaving a space along the sides and ends of the 

 plates equal to their thickness. After the 

 plates have been calked against the joint 

 straps from outside, and then against the 

 plates from inside of the vessel, he fills up the 

 spaces with strips of compressed teak, to 

 which he secures the sheathing with iron or 

 zinc nails (by preference the former), of such 

 a length that, on meeting the iron at the back 

 of the teak strips, the points turn round and are 

 clinched. He concluded by describing plans 

 for applying zinc sheathing to ships built on 

 the ordinary in-and-out strake system, by fill- 

 ing the spaces between the out-strakes by teak- 

 planks equal to their thickness. By this 

 means a flush side is formed, and the sheath- 

 ing can readily be nailed on, and the nails 

 clinched as shown above. He also suggested 

 that the raised holes of M. Roux's system, and 

 zinc rivets, might be employed for zinc sheath- 

 ing, instead of the methods indicated. 



New Method of making Ferro-Manganese. 

 The following new method of making ferro- 

 manganese on the large scale has been intro- 

 duced by Mr. G. Thomson, of Glasgow. He 

 mixes 30 parts by weight of good common 

 coal with 30 parts of common salt and 100 

 parts of manganese-ore, using ten parts of 

 lime as a flux. The pulverized ingredients are 

 then heated to about a white heat in a rever- 

 beratory or other furnace. By this process 

 considerably less carbonaceous matter is re- 

 quired than by any other method. The use 

 of the common salt is to prevent the access of 



air to the metallic manganese, and, if it ap- 

 pears likely, as the operation proceeds, to be- 

 come all volatilized before the smelting is com- 

 pleted, more of the salt must be added in or- 

 der to maintain the protective covering layer. 

 Another method is to add the manganese in 

 the spongy or metallic state, as obtained by 

 the first process, to the iron or steel, the latter 

 being in a fused state, but the combination 

 may also be made by adding the iron or steel 

 to the manganese in the furnace in which the 

 latter has been reduced. A valuable ferro- 

 manganese is also formed by fusing the spongy 

 or reduced manganese with any desired pro- 

 portion of iron in the spongy state obtainable 

 by various well-known processes of reduction, 

 the metals being in all cases covered by a layer 

 of fused salt. 



Sherman's Process. A writer in the En- 

 gineer, commenting on this process, gives his 

 opinion that the iodine used in it has no effect 

 whatever. He thinks that the whole virtue 

 of the process lies in the potassium, because, 

 at the temperature present in the converter 

 and the puddling-furnace, it is quite possible 

 that all the iodine simply escapes as vapor, 

 and that an alloy of iron and potassium is 

 formed which, reacting on the phosphide of 

 iron, forms a phosphide of potassium that re- 

 mains entangled in the metal, and does little 

 harm. If this theory is correct, he reasons that 

 as good results would be obtained by injecting 

 a few ounces of carbonate of potash through 

 a Bessemer converter as can be had from the 

 use of the iodide of potassium employed in 

 the Sherman process, but he has not tested 

 that theory by experiment. He points to the 

 following analyses of Bessemer steel after be- 

 ing treated by the Sherman process, to prove 

 that the iodine does not remove all the phos- 

 phorus : 



The phosphorus was here reduced nearly 

 one-half, but the author remarks that it is 

 highly probable that a similar reduction would 

 have taken place whether the potassic iodide 

 had been used or not, and, as it is, quite 

 enough remains to impair the quality of the 

 steel if the element retains its normal activity. 

 Other authorities, however, regard the Sher- 

 man process with favor, and deem the iodine 

 an essential element in the success of its oper- 

 ation. Much of the criticism to which it has 

 been subjected comes from the champions of 

 rival processes. 



Berartfs Process. A new process appears 

 in the field, as a rival of Bessemer and the 

 others well known, proposing to manufacture, 



