534 



METALS. 



In reference to the minute quantity deposited 

 upon the gold disk, it was found by numerical 

 calculation that the proportion was certainly not 

 more, relatively to the surface of the disk, than that 

 which the remainder of the gold bore to the extent 

 of the surfaces upon which it had affixed itself. 



2. The same experiment repeated, but vessel and 

 contents not darkened. Same results as before. 



3. Gold solution reduced to half its strength, and 

 time of total deposition extended to four months. 

 Diffused sunlight admitted. 



4. Soluble organic matter used in place of wood; 

 sunlight excluded. Time of total deposition of gold 

 two months. 



No discernible difference in results upon point in 

 question to those obtained in experiment No. 1. 



So far, therefore, as is shown by these results, gold 

 reduced from solution of its chloride by aid of such 

 kinds of organic matter as cork or wood does not in 

 the manner of its deposition exhibit such a notable 

 selective power for metallic gold as the description 

 of Mr. Daintree's results would lead us to suppose. 

 It does not, indeed, show any such selective process 

 at all, that is, to a greater extent than can be attrib- 

 uted to the action of surfaces generally regardless of 

 their nature ; and, in support of this, I believe I am 

 correct in stating that the whole sum of our expe- 

 riences (omitting those of Mr. Daintree) is directly 

 against this theory, as to the rapid and marked 

 deposition of gold on gold in the manner stated ; in- 

 deed, so far as I am aware, we only produce by 

 these means fine incoherent p_owder minute crys- 

 tals or films of exceeding thinness nothing nug- 

 gety. We get a certain size of grain or crystal, or a 

 certain thickness of film, which our efforts have 

 hitherto failed to enlarge. 



Gold Assays. A committee appointed by 

 the British Association for the Advancement 

 of Science, to investigate the subject of gold 

 assays, report some interesting facts concern- 

 ing the accuracy of the results obtained in the 

 commercial process. The committee insti- 

 tuted a series of experiments for the purpose 

 of discovering to what extent the weight of 

 pieces of pure gold and of alloys of known com- 

 position would be affected by submitting them 

 to the process of assaying, and consequently 

 how far the results of assay operations were 

 trustworthy. These results showed that the 

 maximum error was only 0.001 per cent, of 

 the original weight of the assay piece, and con- 

 sequently that the results obtained by assaying 

 gold, represented the composition of the por- 

 tion of metal under examination to the 10 ft 60 

 part, a fact which would doubtless appear re- 

 markable to all who were accustomed to the 

 ordinary methods of quantitative analysis. The 

 committee were not unmindful that, although 

 it was possible to attain this high degree of 

 accuracy, it was nevertheless well known that 

 a comparison of the assay reports of different 

 analyses as to the composition of the same 

 might often disclose discrepancies of - 10 g 66 

 parts. Portions of metal from nineteen gold 

 ingots were assayed by the assistant assayer, 

 and were then sent to five other assayers, each 

 of whom furnished an independent report. The 

 discrepancies in their reports varied from y^f^ 

 parts to one part of fine gold in 1,000 of the 

 alloy, or an average deviation of i 6 g 6 6 - parts. 



Alloys. -An alloy of copper, lead, tin, and 

 zinc, the invention of Mr. J. E. Jacoby, of 



Hauiburg-on-the-Heights, Germany, designed 

 for the reduction of friction in the working 

 parts of machinery, is highly spoken of. The 

 proportions of the different metals entering into 

 its composition are : copper, varying from 70 to 

 73 per cent. ; lead, from 15 to 20 per cent. ; tin, 

 from 9 to 11 per cent. ; and zinc, in very small 

 proportions, from 1 down to 00.5, or ^ per cent. 

 A new form of phosphor-bronze, intended 

 far the same purpose as the above, has been 

 introduced by Dr. Kunzel, one of the original 

 discoverers of that now celebrated alloy. The 

 subjoined description is given in Iron: 



"When phosphor-bronze is combined with a cer- 

 tain fixed proportion of lead, the phosphorized triple 

 alloy, when cast into a bar or bearing, segregates 

 into two distinct alloys, one of which is hard and 

 tough phosphor-bronze, containing but little lead, 

 and the other a much softer alloy, consisting chiefly 

 of lead, with a small proportion or tin and traces of 

 copper. The latter alloy is almost white, and, when 

 the casting is fractured, it will be found nearly equal- 

 ly diffused through it ; the phosphor-bronze alloy 

 forming, as it were, a species of metallic sponge, all 

 of whose cavities are occupied by the soft metal alloy 

 segregated from it. This phenomenon of the segre- 

 gation into two or more alloys of combinations of cop- 

 per with tin and zinc has long been known, and from 

 the. fact that such separation is generally massive, 

 and not equable throughout the mass, it has been a 

 source of great annoyance to the founder. Dr. Kun- 

 zel, however, seems to have succeeded in causing, 

 the segregation to take place in uniform distribution 

 throughout the casting, and has taken advantage of 

 the properties of the product which he obtains in 

 this manner, to construct therefrom bearings of rail- 

 way and other machinery. 



A new white metal has just been invented by 

 M. Delatot, with the object of replacing those at 

 present in use at a much less cost. The composition 

 of the metal is as follows : Pure red copper, eighty 

 parts; oxide of manganese, two parts; zinc, eighteen 

 parts ; phosphate of chalk, one part. The mixing is 

 effected thus : To the melted copper is added the 

 oxide of manganese in very small quantities at a time. 

 When the oxide of manganese is dissolvod in the 

 copper, the phosphate of chnlk is added similarly 

 in small quantities. After this reduction has lasted 

 about half an hour, the scoria which floats on the 

 metallic bath must be skimmed off and then the 

 zinc added, about ten minutes before running the 

 metal. This will give a white hard metal, equal to 

 gun-metal in tenacity and resistance, and superior 

 in obviating friction, and can be made at a less cost. 

 In order to accelerate the fusion of the oxide of man- 

 ganese, a flux may be used of the following composi- 

 tion : half part of fluoride of calcium, half part of 

 borate of soda, and one part of charcoal. 



A metallic alloy, claimed to approach more 

 closely the appearance and properties of silver 

 than any heretofore.produced, is also described 

 in Iron : 



The new alloy is a compound of copper, nickel, 

 tin, zinc, cobalt, and iron. The following propor- 

 tions are said to produce a very white metal, per- 

 fectly imitating silver: copper, 71.00 parts; nickel, 

 16.00; cobalt, 1.75; tin, 2.50; iron, 1.75; zinc, 7.00. 

 A small portion of aluminium, say about 1.5 per 

 cent., may be added. The manufacture is, as might 

 be expected, from the alleged fact of the alloy pos- 

 sessing the specific gravity of silver, rather peculiar. 

 " The first step is to alloy the nickel with its own 

 weight of the copper, and add zinc, in the propor- 

 tion of six parts to ten of copper. The nickel alloy, 

 the iron, the rest of the copper, the cobalt in tho 



