530 



METALS. 



Preservation of Iron. Several methods for 

 preventing the rust or corrosion of iron sur- 

 faces have been published during the year. 

 Mr. E. A. Fisher, of San Francisco, offers the 

 following as not only an excellent means of 

 preventing the wasting away of iron and steel 

 by corrosion, oxidation, and other similar 

 causes, but as specially adapted to the preven- 

 tion of incrustation in water tuyeres and steam- 

 boilers. His method is to bring in direct con- 

 tact with any iron or steel surfaces exposed to 

 the action of any natural water, or aqueous, 

 saline, or other solution, some metal or metal- 

 lic alloy that is more easily oxidized, corroded, 

 or eroded, than either iron or steel, and which 

 also forms an oxide insoluble in water. The 

 metals which may be used for this purpose, 

 either separately or in combination, are, ac- 

 cording to the inventor, aluminium, antimony, 

 cadmium, lead, magnesium, mercury, tin, and 

 zinc. 



M. Stanislas L. Delatot, a chemist of Paris, 

 originates an improvement in the manufacture 

 of iron and steel, by the combination of nickel 

 or cobalt, separately, or as a mixture of the 

 two, in definite proportions, with iron or steel ; 

 the effect of which is stated to be that the iron 

 or steel is thereby rendered inoxidizable, i. e., 

 proof against deterioration by rust through ex- 

 posure to moisture, atmospheric or other oxid- 

 izing influences. Cast-iron, so treated, is ca- 

 pable of conversion into wrought-iron arid 

 steel, by means of the ordinary and well-known 

 processes, producing an excellent quality of 

 metal. 



A composition for coating the surfaces of 

 metals, in order to prevent oxidation, has been 

 patented in Florence, and is highly recom- 

 mended. This is composed of quartz, of a 

 suitable " solvent," such as carbonate of pot- 

 ash, and metallic oxides, such as oxide of lead 

 or oxide of cobalt, in equal proportions, the 

 selection of the oxide being made according to 

 the color to be given to the composition ; and 

 the other components also vary according to 

 the metals to be operated upon and the quality 

 of the composition or varnish required. These 

 ingredients are first reduced to fine powder, 

 water is added so as to form a mixture of the 

 consistence of paste, of which a layer is applied 

 with a brush on the surface of the articles 

 (previously cleaned and dried) to be varnished 

 or protected, and, this done, they are exposed 

 to the open air to dry. The articles are after- 

 ward placed in cast-iron or fire-brick muffles, 

 and heated, in kilns of suitable construction, 

 to 800 C. The heat acting on the mixt- 

 ure of silica and metallic oxides causes their 

 combination, at the same time fixing them 

 firmly on the surface of the metals. On being 

 gently cooled and taken out, the metal is cov- 

 ered with a polished silicate or glass, which 

 is said to resist the impact of hard bodies 

 without scaling or cracking. This composition 

 is applicable to many metals, but more espe- 

 cially and with the greatest advantages to cast 



and wrought iron, which by this means may, 

 through their low price, be employed for many 

 articles now made of copper and tin. Iron 

 thus treated becomes coated with a silicate of 

 iron, and may be exposed in very damp places, 

 and even immersed in water, without un- 

 dergoing any oxidation. It is suggested that 

 this process may be employed for protecting 

 ships' armor-plating, and other iron used in 

 ships. 



Spongy Iron as a Water- Purifier. Duringthe 

 past year Prof. Gustav Bischoff, of Glasgow, has 

 been studying the properties of spongy iron 

 with a view to its employment as a water-puri- 

 fier. He finds 1. That spongy iron decom- 

 poses water even distilled water which has 

 been previously boiled ; 2. It reduces nitric acid 

 to ammonia ; 3. It is capable of decomposing 

 nitrogenous organic matter, and reduces con- 

 siderably the amount of organic carbon in water 

 filtered through it ; 4. A minute but almost 

 constant quantity of the iron is dissolved by 

 the carbonic acid present in the water when it 

 passes through the filter, ferrous carbonate 

 being formed. This, however, is soon oxidized 

 and precipitated ; 5. The purification of water 

 increases slightly for some five or six hours 

 after the filtration through spongy iron has 

 been completed ; 6. If the iron is prevented 

 from dissolving by adding to the water before 

 filtration a minute quantity of sodium carbon- 

 ate, its purifying action on the water is con- 

 siderably diminished ; 7. The purifying influ- 

 ence exerted by spongy iron on water contain- 

 ing organic matter is more energetic in hot 

 weather than in winter, when the temperature 

 of the water is frequently below the point at 

 which fermentation almost entirely ceases. 

 The author says : 



These facts appear to confirm my opinion, ex- 

 pressed on former occasions, that the action of 

 spongy iron on impure water is twofold namely, 

 chemical and mechanical. The chemical action 

 must be found in its decomposition of water, to 

 which is probably owing, in part at least, the de- 

 composition of nitrites and nitrates, and the direct 

 combination of nascent hydrogen with the nitrogen, 

 to -form ammonia. The readiest explanation for the 

 decomposition of water is the intimate contact be- 

 tween electro-positive and electro-negative bodies, 

 such as metallic iron and carbon, or even metallic 

 iron and any ferric-oxide which has escaped re- 

 duction ; and it may be well supposed that, conse- 

 quent to the galvanic current thus produced, the at- 

 mospheric oxygen dissolved in water is ozonized, 

 and caused to act as a powerful oxidizing agent. I 

 am driven to this conclusion from the results of a 

 large number of analyses made before and after fil- 

 tration through spongy iron, which, notwithstand- 

 ing the fact of the reduction of nitrates and nitrites, 

 also clearly indicates an oxidizing action shown by 

 the increase of nitrates after filtration. This in- 

 crease is mostly considerable up to twice the 

 original quantity while sometimes there is also a 

 decrease. 



Prof. Bischoff further states that water im- 

 pregnated with lead is thoroughly purified 

 by filtration through spongy iron. A sample 

 of water containing 0.175 grains of lead to the 

 gallon was passed through one of these filters, 



