MI-TAI.S. 



., liidi must have been expected M the 

 result of the- decomposition ot the JM 

 under thc-o conditions. This fact appeared to 

 cl.-arly |...int out tliat tin- theory of silicon 



- iiitiiitittcly mirtd \\iih pig-iron was un- 



V. at toast as regarded this particular 



. hich was a No. 1 Bessemer iron, contain- 

 ing 4.til'J pi-r cent, of silicon, and was thero- 



ii. 't at nil unlikely to contain silicon in 

 admixture, if the. element ever occurred in pig- 

 iron in such a condition. As far as ho was 

 aware, n<> experiments had been made with 

 : ot' proving that silicon existed in a 



ot .-on, Mnatioii in pig-iron, although he 

 believed it was the generally received opinion 



such was the case. He had therefore 

 made a considerable number of experiments 

 with the view of ascertaining how far this con- 

 clusion was correct. After detailing the vari- 

 ous experiments to prove his theory, he went 

 on to say that from these results it must fairly 

 be concluded that the silicon contained in pig- 

 iron did not exist in a state of mechanical 

 mixture, but existed combined with a portion 

 of the iron as a silicide of iron, in the same 

 manner that carbon existed as a carbide of 

 iron, only differing from carbon in so far that 

 it did not exist in a graphitoidal form in pig- 

 iron. If the pig-iron used had contained any 

 uncombined silicon it would have been found 

 in the insoluble residue from the experiments 

 with Nordhausen sulphuric acid and hydro- 

 iluoric acid, as it was insoluble in even the 

 lesser acid, after being strongly heated; and 

 as an uncombined silicon must have been heat- 

 ed intensely in the blast-furnace, there could 

 be little doubt that, as a rule, pig-iron did not 

 contain any uncombined silicon. In conclusion, 

 it must fairly be considered, from various ex- 

 periments ho had made, that silicon was not 

 contained in pig-iron in a state of mechanical 

 mixture (except, perhaps, under peculiar cir- 

 cumstances), but as a chemical constituent. 



Extraction of Iron from Pyrites Refuse. 

 In the manufacture of sulphuric acid from iron 

 pyrites a large amount of refuse, containing a 

 high percentage of -iron, has hitherto gone to 

 waste, owing to the difficulty of separating the 

 metal from the sulphur which remains. Some 

 experiments, with a view to the extraction of 

 the iron in available shape, have lately been 

 made by Dr. Hoffmann, who claims to have 

 reached a successful result. His experiments 

 were made with the pyrites from the Meggen 

 mines in Germany, the source of supply for 

 nearly all the German manufactories of sul- 

 phuric acid. The residuum of sulphur, always 

 in considerable quantity, renders the iron nearly 

 useless for any practical purposes. The efforts 

 of chemists have been directed toward remov- 

 ing the sulphur completely from the refuse, 

 and that could be done by long-continued heat- 

 ing, along with abundant introduction of air. 

 Dr. Hoffmann has repeated, these experiments 

 under the most favorable conditions, but he 

 has always found that the sulphur is peculiarly 

 VOL. xiv. 34 A 



difficult to remove from the refuse of the Meg- 

 gen pyrites, much more so than elsewhere. 

 included that tin- composition mast be 

 quite different ; and, submitting the KU balance 

 to chemical analysis, he found in it, besides 

 Kulphnr, iron, selenium, arsenic, lead, mercury, 

 and thallium, considerable quantities of /inc. 

 in the form of zinc-blende; various specimen - 

 contained over 6 per cent. zinc. The presence 

 of this metal explains the difficulty of expelling 

 the last traces of sulphur. By lixiviation th< 

 zinc is got rid of, and the refuse afterward falls 

 down into a fine powder, which, however, still 

 contains lumps that appear to have been little 

 affected by the previous roasting. These lumps 

 hold large quantities of sulphur, and have, 

 therefore, to be removed, which is done by 

 sifting, when the powdery portion is ready for 

 the separation of the iron in the ordinary way. 



Strength of Iron increased ly Strain. In the 

 course of some experiments on the tensile 

 strength of iron made by Prof. Thnrston during 

 the past year, in Washington, it was observed 

 that when subjected to heavy strain, even to 

 the point of apparent weakening, and then al- 

 lowed to rest for a time, iron not only regained 

 its original strength, but actually became 

 stronger than before strain was applied. At- 

 tention was called to this fact in the following 

 way : A piece of iron was being subjected to 

 tensile strain by means of an eye welded to 

 each end of the piece. When the limit of 

 strength was apparently reached, and a sensi- 

 ble contraction of the circumference indicated 

 that the piece was about to break, the weld 

 holding one of the eyes gave way, and caused 

 a postponement of the test until the next day, 

 the eye having, in the mean time, been welded 

 on again. On renewing the test the iron, in- 

 stead of parting at the weakened spot, as was 

 expected, sustained an additional strain of 

 20,000 pounds, and then parted at the other 

 end, where no signs of weakness had before 

 been observed. The weakened part had thus 

 actually gained in strength during its period 

 of rest. This remarkable result was confirmed 

 by subsequent experiments. And it was also 

 shown that the longer the rest after strain the 

 greater was the increase of strength. 



Restoration of Burned Steel. The following 

 simple process for the restoration of burned 

 steel is described in Iron by Mr. J. L. Daviea, 

 Swansea' Wales. A mixture consisting of one 

 part by weight of the residue of paraffine- 

 stills with four parts by weight of resin-oil, 

 is the preparation employed. The burned 

 steel is first heated red hot and then plunged 

 into this fluid, where it is allowed to remain 

 for a few seconds; it is then reheated and 

 cooled in the ordinary way. Experience in 

 the use of this preparation will quickly enable 

 persons to give any desired temper to their 

 tools, and the) may be made especially hard by 

 heating them red hot, dipping into the liquid, 

 and then reheating to a slightly white heat, and 

 immediately afterward cooling in pure water. 



