430 



METALLURGY. 



finished piece from a block of steel of considerable 

 size. When the large rolling mills of the country 

 changed their product from iron to steel, they con- 

 tinued to use the small hammers with which their 

 forges were equipped, which, by taking advantage 

 of the property of welding possessed by wrought 

 iron, were of sufficient capacity to build up such 

 small forgings of that metal as were demanded, but 

 were not powerful enough to reduce properly the 

 large blocks of steel it was necessary to work upon ; 

 and there were other reasons, in view of the processes 

 which are now considered necessary for turning out 

 good work, why the proper equipment could not be 

 supplied by the forges of the day. The author 

 supports his position by citing a number ot speci- 

 men defects met in practice in steel forgings 

 which have caused their failure in the past and 

 have prevented their coming into more general use 

 all due to faulty methods of manufacture. 



In the light of seventeen years' observation in 

 the use of the Post steel cross'ties on the Liege and 

 Lindbourg (Holland) state railway. Ilerr Renson, 

 chief engineer, concludes that the life of a steel tie 

 exceeds several times that of those of oak. Cracks 

 and breaks in steel ties noted in the beginning 

 were due to the fact that the holes for the fasten- 

 ings were punched. When the holes were drilled 

 the evil disappeared. A plate placed between rail 

 and tie, and raised edges along the top of the tie, 

 further increased the durability of the latter. With 

 these ties there was also less fear of the rails spread- 

 ing. 



To protect marine boilers in the French marine, 

 the boilers are filled with fresh water to which milk 

 of lime or solution of soda is added, strong enough 

 to neutralize any acidity of the water. It may be 

 stronger in boilers with large tubes than in those 

 with small, where the deposit from the solution 

 may be liable to contract, the effective area. Care 

 must be taken tb preserve the outside of the steel 

 crown in these boilers which are not to be used for 

 long periods. For this purpose they are painted 

 with red lead or coal tar as far as it is possible to 

 reach, while a protective coating is obtained for the 

 inaccessible parts by burning coal tar under the 

 tubes. The smoke forms a coating of soot which 

 prevents the air from reaching the surface of the 

 tubes. Quicklime is put inside of the boiler casing, 

 and it is closed and made air-tight. 



Magnets are used at the plate mill of the Illinois 

 Steel Company to lift red-hot metal. They are 

 capable of lifting each five tons of red-hot steel, 

 and are also so adjusted as to pick up half a dozen 

 Mcd plates and drop them one at a time. 



Gold and Silver. Dr. Thomas Ewan points out 

 that an advance of importance in the metallurgy 

 of gold is marked by the application of electrolysis 

 in the precipitation" from cyanide liquors. Gold 

 is not precipitated in a reasonable time by zinc 

 from solutions containing less than 0.1 or 0.2 per 

 cent, of free potassium cyanide, whereas with the 

 electrolytic process the concentration of the solu- 

 tion is a matter of indifference. It thus becomes 

 possible, by the employment of very dilute cyanide 

 solutions, to extract economically the small qnan- 

 tities of gold contained in slimes and tailings which 

 would otherwise have been thrown away. A fur- 

 ther advantage of the electrolytic precipitation is 

 that the metal obtained contains about 89 per cent, 

 of gold, instead of the 70 per cent, contained in the 

 zinc bullion. 



The Bromine Gold Extraction Company is repre- 

 sented to have succeeded in treating ore with a loss 

 of only about half an ounce of bromine to the ton 

 of ore treated. The ability to recover the bromine 

 at a small loss and a small nominal cost over- 

 comes the chief objection to its use. The bromine 



is converted into a dry salt, and shipped in that 

 form to any part of the world. The company has 

 succeeded in treating ores containing both gold and 

 copper with success, at a low cost and a saving of 

 both metals. 



In the Black permanganate gold recovery process, 

 now coming into use in the mines of New Zealand, 

 sulphuric acid, together with common salt in com- 

 bination with permanganate of potash, take the 

 place of the hydrochloric acid of the Etard solu- 

 tion, and the solution is said to accomplish the work 

 of extraction equally well and more rapidly, while 

 it is much cheaper. An extraction of 92 per cent, 

 of the gold contents of the ore has been effected 

 with the Black solution in fifteen hours by percola- 

 tion and in five hours by agitation. 



For the assay of silver by Gay-Lussac's humid 

 process, as described by Mr. A. C. Outerbridge, the 

 assayer prepares two solutions of common salt, one 

 of which is known as the " normal solution " and 

 the other as the "decimal solution." One begins 

 and the other completes the assay. The sample is 

 weighed out in quantity sufficient to contain not less 

 than one gramme of pure silver, and is then placed 

 in a glas' bottle with a charge of nitric acid. The 

 acid is caused to boil, and the silver alloy is com- 

 pletely dissolved in a short time. A charge of the 

 normal salt solution is allowed to flow into the bot- 

 tle from a glass pipette, which is made of such a 

 capacity that it shall contain just enough salt water 

 to precipitate one gramme of pure silver. The chlo- 

 rine in the salt combining instantly with the silver, 

 precipitates it in the form of a white cloud ; the 

 bottle is agitated rapidly for a few moments, when 

 the precipitate settles to the bottom, leaving a clear 

 solution above. The assayer next allows a charge 

 of the "decimal solution," which is one tenth the 

 strength of the normal solution, to flow into the bot- 

 tle from a burette or glass tube with graduated divi- 

 sions, each division making one hundredth the 

 capacity of the large pipette. If any silver remains 

 in the solution, a cloud will be observed on the sur- 

 face. Now, as this decimal charge is one tenth the 

 strength and one hundredth the volume of the large 

 pipette, it will, of course, precipitate one thousandth 

 as much silver, or one milligramme. The bottle is 

 again agitated to settle the precipitate, and suc- 

 cessive charges of the " decimal solution " are added 

 until all the silver is precipitated, and then a sim- 

 ple rule-of-three calculation gives the exact pro- 

 portion of pure silver contained in the original 

 weight of the alloy. 



The electrolytic process of Messrs. Pclatau and 

 Clerici for extracting gold and silver from their 

 ores and other compounds has been described as a 

 single, continuous process, because it has proved 

 itself equal to effect in one operation all that can 

 be expected of it. In it we have, Major-Gen. C. E. 

 Webber believes, for the first time a process and 

 apparatus which effectively combine in a way that 

 can be constructed and worked by a workman of 

 average intelligence, a vat made of material di- 

 electric in its nature ; an agitating apparatus of 

 various specific forms, each form calculated to carry 

 out one and the same process, having an agitator, 

 part of which constitutes the anode in an electro- 

 lytic circuit, which is carried so that it can not 

 make contact with the bottom or sides of the vat : 

 the presence of a cathode, covering the whole of the 

 bottom of the vat, made of a metal and adapted to 

 carrying on it a layer of mercury ; the use of a 

 graduated current from an electrical generator, hav- 

 ing large quantity and low potential : and the mix- 

 tureor sludge under treatment composed of water in 

 given proportions, ore finely pulverized, potassium 

 cyanide or other solvent of gold and silver, and 

 common salt, with the addition as required during 



