104 



SCIENCE. 



(Vol. I., No. 4. 



ceased to decompose at all; when, on examining it, 

 he noticed that it was coated with a kind of enamel. 

 It at once occurred to him that tlie process in ques- 

 tion might be used to obtain such a coating; but he 

 found, after a few days' exposure of tlie iron to the 

 atmospliere, tliat tlie coating scaled off, and he pur- 

 sued tlie matter no farther. The iron employed in 

 this case was rusty ; but if it iiad been new, my father 

 would in all probability liave been the accidental 

 author of the process which Professor Barff discov- 

 ered ten years latei'. That consists in subjecting iron 

 or steel articles to the action of superheated steam ; 

 and, when they are at a temperature sufficiently high, 

 tlie following chemical change takes place : 3 Fe -|- 

 4 (n.2 O) = Fe;j O4 -I- 8 H. My father thought that 

 what Professor Barff could effect with steam, he 

 might also effect with air; and experiments were 

 made varied both in character and results. On con- 

 sidering the fact that air Is oxygen and nitrogen in 

 mechanical combination only, I came to the conclu- 

 sion, that, to form the lower or magnetic oxide, the 

 quantity of free oxygen, and so of the air employed, 

 must bear some proportion to the surface of the arti- 

 cles exposed to its action, more especially when a 

 comparatively low heat is employed ; and it has been 

 found tliat the quantity of air passed through the 

 retort during most of the unsuccessful experiments 

 was three hundred or four hundred times more than 

 was actually necessary. The mode of action I adopted 

 was to admit a few cubic feet of air into the retort 

 at the commencement of every half-hour, and then 

 leave the iron and air to their own devices; the re- 

 tort, of course, being tiglitly closed. During each 

 half-hour a coating of magnetic oxide was formed, 

 and the operation was repeated as often as was con- 

 sidered necessary. Tbis was effective, but costly; 

 both this and the Barff process requiring the exter- 

 nal heating of the chamber. Successful experiments 

 were made with air, but open to the same objection 

 in regard to cost. Experiments with carbonic acid, 

 produced by the decomposition of chalk, which should 

 give 3 Fe -t- 4 (C O2) = Fc, 0+ -f- 4 (C O), gave a coat- 

 ing of light color and easily removed; the film iiroba- 

 bly being a mixture of Fe O and Fes O4, or something 

 nearer the metallic state than is magnetic oxide. But, 

 even if successful, the cost of this method would still 

 be too high. I therefore proposed to use a fuel gas- 

 producer, similar in principle to the Siemens gener- 

 ator, but altered to suit other requirements; to burn 

 the combuslible gases thus produced, with a slight 

 excess of air over and above that actually required for 

 perfect combustion, and to heat and oxidize the iron 

 articles placed in a suitable brick chamber by these 

 products of combustion. 1 also arranged a continuous 

 regenei'ator of fire-clay tubes underneath the furnace ; 

 so that the products of combustion, leaving the oxidiz- 

 ing chamber, passed outside the tubes, imparting a 

 portion of the waste heat to them, which was taken 

 up by the in-going cold air passing through their 

 interior on its way to the combustion-chamber. I had 

 hoped in this way to be able to so regulate the excess 

 of air over that required for complete combustion, as 

 to be able to produce magnetic oxide direct, instead of 

 the lower and useless oxide or combination of oxides. 

 I obtained some beautiful results, and some again 

 were unaccountably bad; and I soon found that it 

 was as diflicult to regulate the precise amount of oxi- 

 dation as it first was in the Bessemer process. But I 

 was fortunate enough to hit upon an .ilmost parallel 

 remedy; that is to say, I increased the quantity of 

 free oxygen mixed with the products of combustion, 

 and_ oxidized the iron articles to excess during a fixed 

 period of generally forty minutes, when magnetic 



oxide was found close to the iron, and sesquioxide 

 over all. Then for twenty minutes I closed the air- 

 inlet entirely, leaving the gas-valve open, and so re- 

 duced the outside coating of sesquioxide to magnetic 

 oxide by the reducing action of the combustible gases 

 alone. 



The Barff patents have been purchased by my 

 father. His process is better than ours for wrought 

 iron, and perhaps for polished work of all kinds, as. 

 iron commences to decompose steam at a very low 

 temperature, — in fact, much below visible redness. 

 For ordinary cast iron, and especially that quality 

 which contains much carbon, the Barff process is 

 much too slow in its action; and some specimens that 

 I have treated in England have taken as many as 

 thirty-six hours to coat effectually, which could read- 

 ily have been finished off in five hours by the Bower 

 process. The main distinction between the two is, 

 that the Bower is much more energetic in its action. 

 The objection to the use of a closed mufiie externally 

 heated in the Barff process has been almost entirely 

 overcome by simply putting wrought iion into a 

 Bower furnace previously well heated, then shutting 

 off both the gas and air sifpplies, and admitting steam 

 into the regenerator tubes. Steel, I consider, can be 

 equally well treated by both processes; except polished 

 steel, which is better treated in a low-temperature 

 Barff furnace. Of the fuel burnt in the gas-producers, 

 anon-caking coal is the best. Virginian splint has 

 suited very well in this country; and of this about 

 one ton every three days is required for a furnace 

 with an oxidizing chamber 13 feet long aiul 4 feet 

 3 inches wide and high. When a gas-coal is employed, 

 it should be fed through the charging hoppers just 

 before each deoxidizing operation, when a smoky 

 flame is of great advantage. I have, however, dis- 

 covered that anthracite coal can he used as well as a 

 gas-coal by simply allowing petroleum to drop, at the 

 rate of one gallon per hour, upon the red-hot surface 

 of the coal in one of the producers. This method 

 has been exclusively used in this country. 



Tliese magnetic-oxide processes not only protect 

 from rust, but the coating is of such a beautiful color 

 as to render articles I'eady for the market directly 

 Ihey are out of the furnace and cooled. One remarka- 

 ble feature of these is, that there is no more cost 

 (except in the labor of handling ilieni) in treating 

 2,24U articles each weighing a pound than in coating 

 a cube of the metal weighing a ton; and so pene- 

 trating is the process, that every cjevice, no matter 

 how intricate the pattern may be, is as effectively 

 coaled as the plainest surface. There is absolute 

 certainty that paint used on iron so coated will adhere 

 as well as on wood or stone; and thus iroli maybe 

 used for construction work in a thousand directions 

 in which it has not up to the present time been pos- 

 sible on account of its liability to rust, no matter 

 wliat the coating used to protect it has been. Manu- 

 facturers appear far more ready to apjily the processes 

 here and on the continent of Europe than, up to 

 now, they have been in England; but perhaps the 

 reason has been, that, so far as Professor Barff's 

 process is concerned, it has only jtist been shown 

 how large masses can be dealt with by the use of 

 the Bower furnace. For ordinary hollow-ware for 

 kitchen or table use, whether of cast or wrought 

 iron, the process is admirably adapted. It is in- 

 tended to apply the process to cast-iron gas and 

 water pipes; and, as the former have comparatively 

 little pressure to bear, they may be m.ade nuich light- 

 er if rendered incorrodable: wliile, for water, there 

 is no reason now wliy wrought-iron or mild steel 

 pipes should not be used. lu the case of railway- 



