486 



METALLUEGY. 



An easy method of cleansing iron from rust 

 is described, by which the article, even if it 

 is much eaten into, is greatly improved in ap- 

 pearance. It is immersed in a nearly saturated 

 solution of chloride of tin, and the duration of 

 the immersion is regulated by the greater or 

 less thickness of the film of rust; in most 

 cases, however, from twelve to twenty-four 

 hours will suffice. The solution of chloride of 

 tin must not contain too great an excess of acid, 

 or it will attack the iron itself. After the arti- 

 cles have been removed from the bath, they 

 should be washed in water, and then with am- 

 monia, and dried as quickly as possible. Arti- 

 cles treated in this manner assume the appear- 

 ance of dead silver. 



Miscellaneous. A process has been described 

 for casting iron and other metals upon laces, 

 embroidery, fern leaves, and other combustible 

 materials, including even the most delicate 

 fabrics. When this is done, the tissue is not 

 injured or disturbed at all, but is perfectly car- 

 bonized into a very refractory carbon, while 

 there is produced on the casting a sharp and 

 accurate mold of the design, which may be 

 used as a die. In one experiment, a piece of 

 lace, having open meshes a little larger than a 

 pin's head, was suspended in the mold, so as 

 to divide it into two equal parts. The molten 

 metal was then poured in on both sides of the 

 lace. When the casting was cold, it was 

 thrown upon the floor of the foundry and sep- 

 arated into two parts, while the lace fell out 

 uninjured. The pattern was reproduced upon 

 each face of the casting. The question natu- 

 rally arises, why did not the iron run through 

 the holes and run together ? The answer is 

 found by Mr. A. E. Outerbridge, in the fact 

 that the thin film of oxide of iron or " skin," 

 which always forms on the surface of molten 

 iron, was caught in the fine meshes, and thus 

 prevented the molten metal from joining 

 through the holes. The author's experiments 

 indicate that to secure this result, the meshes 

 must not be more than about one fiftieth of 

 an inch in diameter. He suggests that the 

 intrusion of particles or globules of particles 

 partly cooled, on which a " skin " has formed, 

 may furnish the explanation for many of the 

 obscure flaws found in castings. 



A committee of the Franklin Institute, hav- 

 ing examined Mr. Outerb ridge's processes, re- 

 ports that the success of the method of prepa- 

 ration for them consists in first removing the 

 fluid or liquid parts of the structure operated 

 upon, and then so slowly draining off those 

 constituents which are produced by destructive 

 distillation that the carbonaceous parts, which 

 are unaffected by the heat, and the integrity 

 of the fibers or structures of the fabric, shall 

 not be disturbed by the too tumultuous exit of 

 the vapors and gases; the exceedingly high 

 temperature at the close of the treatment in- 

 suring the complete expulsion of all volatiliza- 

 ble matter. By this treatment, an easily igniti- 

 ble material is converted into one exceedingly 



difficult of ignition, while the method employed 

 in casting at the same time secures the pre- 

 servation of the structure with but slight 

 diminution of dimensions. The change in the 

 properties of the material permits the use of 

 woven or natural fabrics as molds for the 

 cheap reproduction in metal of designs which 

 could not otherwise be made, except at enor- 

 mous expense for engraving. The application 

 of the invention in the arts is at present limited 

 to the cheap production of dies for the orna- 

 mentation of castings, or to the production of 

 dies for embossing leather, paper, or metallic 

 surfaces, and also for the easy parting or di- 

 viding of metal in casting ; but new fields of 

 application may be opened when the method 

 is brought into more general use. 



Thomas Turner has been led to conclude 

 from the examination of various methods for 

 determining the hardness of metals, that 

 hardness and tenacity are distinct physical 

 properties ; that methods for the quantitative 

 determination of hardness, depending on the 

 production of an indentation of considerable 

 size, have the disadvantage that the results are 

 influenced by the tenacity of the metal, and 

 that owing to plasticity they vary according to 

 the time taken to produce the indentation ; 

 and that brittle substances are apt to be broken 

 by the pressure ; that in substances which are 

 homogeneous in structure, the hardness and 

 tenacity generally vary according to the num- 

 ber of atoms in a given space ; but that in sub- 

 stances possessing a definite structure the last 

 rule does not apply. 



Having observed that ends of wires were 

 often stuck firmly together after the passage 

 of the electric current, Mr. Elihu Thomson has 

 devised a plan for electric welding, and has 

 constructed suitable apparatus for effecting it. 

 The pieces are prepared for the operation by 

 cleaning those parts with the file or emery, 

 which enter the clamps where the ends are 

 held in place, so that a contact shall be effect- 

 ed. The pieces being placed in the clamps a 

 moderate pressure, tending to hold them in 

 abutment, is applied, and a flux may be added, 

 after which the current is put on. Heating of 

 the abutted ends begins at once, and proceeds 

 with a rapidity depending on the current flow 

 and the size and nature of the pieces treated. 

 With great energy of current, joints on iron 

 bars of over one-half inch diameter have been 

 made in less than three seconds, and with 

 small wires the action is almost instantaneous. 

 The temperature to which the pieces are heated 

 may be kept perfectly under control by em- 

 ploying suitable devices to govern the flow of 

 the current. Consequently, varieties of steel 

 which are easily injured by excessive heating, 

 or which will not bear hammering when hot, 

 may be welded quite readily. Even very fusi- 

 ble metals, such as lead, tin, or zinc, may be 

 welded if resin or tallow or chloride of zinc 

 is used as a flux instead of borax. While or- 

 dinarily it has been the exception that metals 



