METALLURGY. 



removed by washing with water, and the filter 



having been drift! the iron oleatc is run off with 



lint petroleum. 



The peculiar adaptability of aluminum for the 

 roust riK-tiuii of nmfs for train sheds and other 

 similar purpi-si's is pointed out by Alfred K. 

 Hunt. Sheet aluminuin can be furnished with 

 a tensile strength fully equal to that of sheet 

 ei.pper; it can be bent and Hanged readily, and 

 can he fastened together in the same way copper 

 sheets are. The metal is not acted on severely 

 by salt water, and in an experiment made on a 

 sailing vessel at sea a copper sheet corroded more 

 than one of aluminuin under equal exposure by 

 immersion. Harnacles, however, seem to thrive 

 (ut the aluminum plates. Mr. Hunt has also 

 toted aluminum in contact with gases from 

 locomotives, and finds that it lasts remarkably 

 well, being in this respect better than copper, 

 and far superior to iron. It is, however, not ad- 

 visable to use soldered joints either with alu- 

 minum or copper plates, because of the expansion 

 which the metal suffers, which would soon cause 

 the joints to leak. The galvanic action of alu- 

 minum with other metals should also be con- 

 sidered when the question of using it arises. 



The following solders for aluminum are rec- 

 ommended by J. Novel: No. 1, pure tin; melts 

 at 250. No. 2, pure tin 1,000 parts, fine lead 

 50 parts ; melts at from 280 to 300. No. 3, pure 

 tin 1,000 parts, pure zinc 50 parts: melts at 

 from 280 to 300. These three solders may be 

 used in the manufacture of aluminum trinkets. 

 For the following two solders the soldering iron 

 should be made of pure nickel ; no. 4, pure tin 

 1,000 parts pure copper, 10 to 15 parts; melts 

 at from 350 to 450. No. 5, pure tin 1,000 parts, 

 pure nickel 15 parts ; melts at from 350" to 450. 

 No. 6, pure tin 900 parts, pure copper 100 parts, 

 bismuth 2 to 3 parts; melts at from 350 to 

 450, and is recommended for soldering alumin- 

 um bronze. 



The essential features of a new system of elec- 

 troplating with aluminum, according to the 

 'London Electrical Review," are: A solution of 

 ammonia alum in warm water is prepared, con- 

 taining 20 per cent, of alum. To this is added 

 a solution containing about the same quantity of 

 pearlash and a little ammonia carbonate. The 

 mixture results in effervescence and in the depo- 

 sition of a precipitate. The latter is filtered 

 off and well washed with water. A second solu- 

 tion of ammonia alum, containing 16 per cent, 

 of alum and 8 per cent, of pure potassium cya- 

 nide, is now prepared warm and poured over the 

 precipitate previously obtained, the mixture be- 

 ing then boiled for thirty minutes in a closed iron 

 vessel, jacketed to insure uniformity of heating. 

 At this stage about 20 kilogrammes of water are 

 added, and about 2 kilogrammes more of potas- 

 sium cyanide, and the whole is kept boiling for 

 about a quarter of an hour. The liquid is then 

 filtered from the precipitate, and is ready for use 

 in the electrolytic bath. 



Copper and Tin. In the process formerly 

 used for depositing metal in making seamless 

 copper ware, the product was of a crystalline 

 porous nature, and wauling in the qualities of 

 smoothness, tenacity, ductility, and density. It 

 could therefore be used only as thin deposits, 

 such as electrotyping or coating inferior or cor- 



rosive articles. In a new process, adopted at 

 Springfield, Mass., the copper is acted upon by a 

 heavy pressure during deposition, so that every 

 tli in film is treated separately. 



A curious change was observed to have taken 

 place in the brass condenser tubes of a certain 

 sir. -mi vessel after they had been in use rather 

 more than twelve months. The metal was in 

 many places converted into almost pure copper 

 of a spongy texture, while the zinc of the alloy 

 had disappeared. The probable cause of the fail- 

 ure was found to have been an electrolytic action 

 between the tin lining of the tubes and the brass, 

 in which the sea water circulating through the 

 condenser formed the electrolvte. Had the tin 

 coating remained perfect, doubtless no corrosion 

 would have resulted ; but the sand and grit con- 

 veyed in suspension through the condenser car- 

 ried away the tin coating in spots, and it was at 

 these points that the transformation of the metals 

 occurred. If the pipes had not been tinned at 

 all they would probably have remained intact. 



On passing a current of gaseous chlorohydric 

 acid through the refuse of copper-bearing pyrites, 

 heated to a certain temperature, Messrs, Blattner 

 and Koestner found that the acid combined only 

 with the copper, thus making it soluble in water, 

 while a notable proportion of it was decomposed 

 by the action of the pyrites, setting free chlorine. 

 This process, if it can be carried out on a com- 

 mercial scale, will make it possible to extract all 

 the copper remaining in the pyrites, and will 

 serve also for the production of chlorine. 



An experiment by the Arizona Copper Com- 

 pany for the extraction from the tailings from its 

 concentration mill, by means of a sulphuric-acid 

 leaching process, of the copper contained in them, 

 is said to have given such satisfactory results as 

 to warrant the practical adoption of the process. 



To recover copper and nickel from mattes con- 

 taining also iron, J. Strap treats the matte so 

 that the copper is first separated. The residue 

 is then cleared from iron and the nickel depos- 

 ited from it. 



In order to recover tin from tin-plate scrap, 

 J. F. Duke and F. Redman take advantage of the 

 fact that tin has a greater affinity for lead than 

 for iron. The plate is compressed to a compact 

 mass, and then heated to a temperature some- 

 what exceeding the melting point of lead, after 

 which molten lead is poured into the vessel so as to 

 cover the tin plate. The heat being maintained, 

 the lead and tin become alloyed with one another. 

 The alloy which does not adhere is then run into 

 another vessel containing a charge of tin plate 

 heated to the melting point of lead, and so 

 successively through a series of, say, six vessels. 

 More molten lead is then run into the first and 

 through the six vessels, so as to reduce the pro- 

 portion of the tin in the scrap, and a number of 

 charges six, for example are run through the 

 vessels. The alloy of lead and tin obtained from 

 the last vessel can be used as solder or for other 

 purposes, or the two metals can be separated. 



By the process of M. Lambotte, of Brussels, for 

 recovering tin from clippings of tinned iron, the 

 clippings are introduced into a vertical cylin- 

 drical furnace which is surrounded by a spiral. 

 Air charged with chlorine gas passes through 

 the spiral, where it is heated by the chemical ac- 

 tion going on within the furnace, and, entering 



