542 



METALS. 



ing blast, by taking it up and returning it again 

 into the furnace. The calcined ore falls at last 

 into a space below, from which it can be drawn 

 off into wagons, to be transferred to the next 

 operation. 



Among the advantages claimed by the in- 

 ventor for this furnace, are : the large and con- 

 tinually-renewed surfaces exposed by the finely- 

 divided ore; perfect contact of the draught 

 throughout with the ore; regulation of the 

 supply of ore as required ; do. of the supply of 

 air, both in reference to the amount of ore, and 

 also for obviating the effect of storms; and 

 finally, the economizing of waste heat of the 

 blast. It has been questioned whether the cost 

 of pulverizing, of the blast, and of the necessary 

 attention, may not exceed the value of the acid 

 obtained. M. Gerstenhofer states, however, 

 that at the Eoyal Saxon Sulphuric- Acid Works 

 this furnace is now exclusively employed for 

 the roasting of the pyrites used, and with suc- 

 cess. Mech. Magazine, October 6, 1865, etc. 



Saving from Slag of Copper Furnaces. Mr. 

 Spence finds, that besides the loss of sulphur at 

 the Swansea and other copper works, there has 

 been at the former in respect to which he has 

 made examination a rejection of much copper, 

 the slag here containing rarely less than 0.5 

 per cent, of the metal. He has patented the 

 use of a flux which saves a considerable portion 

 of this copper, the flux being simply the spent 

 shale of the alum manufacture the residue of 

 the shale of the coal-measures, after the latter 

 has been acted on by sulphuric acid for the pro- 

 duction of alum. 



Non-metallic Impurities of Refined Copper. 

 Obviously, metallic impurities in copper must 

 exert considerable influence on the quality of 

 the metal; but of these analysis can already 

 detect the smallest traces. Prof. F. A. Abel 

 (London Chem. Society, March 3, 1864) states 

 that of non-metallic elements oxygen is very 

 generally present, and that it is known to have 

 a marked effect on the quality of the copper 

 containing it. Copper being highly oxidable, 

 and its suboxide to a considerable extent solu- 

 ble in the fused metal, the latter, as prepared 

 by the ordinary metallurgical processes, can 

 scarcely be free from oxygen. 



The author had found the process of ascer- 

 taining the quantity of oxygen, by reduction 

 with hydrogen, untrustworthy. He proposes 

 a new one, in which it is only necessary to 

 convert a known weight of copper into its 

 nitrate, by digesting it in an aqueous solution of 

 neutral nitrate of silver: along with reduced 

 silver and soluble nitrate of copper, there is 

 obtained also a quantity of insoluble basic ni- 

 trate of copper, and which is proportional to 

 the amount of suboxide that had been present 

 in the metal. The author gives a mode of 

 treating the products obtained with sulphuric 

 acid the account being too long for insertion 

 in this place and through which the propor- 

 tion of suboxide in any sample becomes known. 



Kapunda copper, a very pure and free arti- 



cle, invariably showed some deterioration from 

 oxygen contained in it, and in amount varying 

 from .12 to .33 of 1 per cent. By prolonged 

 fusion of ordinary copper in a closed crucible, 

 under a layer of charcoal, and allowing the 

 metal to cool out of contact of air, Prof. Abel 

 prepared a copper wholly free of oxygen ; and 

 the metal in this condition possessed remark- 

 able toughness. Samples of " dry " copper 

 showed .42 to .50 of 1 per cent of oxygen, cor- 

 responding to 4.5 per cent, of suboxide. Prof. 

 Abel treats also of carbon, selenium, and sul- 

 phur, as impurities in copper, but of which the 

 amounts are very small. Chemical News, 

 March 12, 1864. 



Coppering of Cast-Iron. M. Dullo presents 

 in Le Technologiste, May, 1865, a method of 

 coppering articles of cast-iron, which (as he 

 states) serves to avoid the imperfections and 

 sometimes even failure liable to follow the 

 ordinary processes in case of that metal, while 

 it is easy of practice, and affords with every 

 sort of cast-iron excellent results. 



The piece to be coppered is first scoured 

 with chlorhydric acid, with very particular 

 care, freeing it of all oxide, and not touching it 

 afterward with the fingers ; and it is then left 

 in slightly acidulated water until the moment 

 of transferring it to the coppering bath. This 

 bath is prepared by dissolving the oxide of cop- 

 per in chlorhydric acid, in the proportions of 

 25 grammes (about J oz. avoirdupois) of the 

 oxide to 170 grammes (nearly 6 oz. by weight) 

 of the acid, and for every such quantity adding 

 1 litre (1.76 pints) of a mixture, in equal 

 parts of alcohol and water. The piece of iron, 

 still wet, is plunged in this bath ; and after the 

 lapse of some hours it will be found quite 

 equally covered with a thick and strongly 

 adhering layer of copper. If the acid of the 

 bath be either too much concentrated or too 

 dilute, the coppering will not succeed, the iron 

 becoming covered with crystals of chloride of 

 copper, or the deposit of the metal occurring 

 speedily but in a thin film only. Alcohol, .a 

 poor conductor of electricity, affords the means 

 of enfeebling at will the galvanic action in the 

 bath in which, generally, certain metals are to 

 be coated with certain others ; so that, up to a 

 certain limit, an increased proportion of alco- 

 hol in the mixture retards the deposition and 

 favors an increase of thickness in the coating; 

 though it is not well to dispense with water 

 altogether. 



An inconvenience sometimes attending the 

 above process is the deposit, over a thin Liver 

 of the copper, of a layer of its chloride, which 

 requires some time to give place to the metal; 

 where haste is important, it may be necessary 

 to remove the piece from the bath, and, with 

 the same precautions as before, to wash it 

 alternately, twice in succession, first with di- 

 lute chlorhydric acid and then with sodu lye, 

 finally drying in a dry place. Objects coated 

 as above described can be covered airain with 11 

 coating of iron nearly as white as silver and of 



