228 ANNUAL OF SCIENTIFIC DISCOVERY. 



charge would become consolidated, and could not be removed. In the new 

 method the jets of air agitate or ' boil ' the fluid iron, and yet this solidifica- 

 tion docs not proceed, and it has been assumed that the acting temperature 

 is so high that the pure iron becomes fluid. No evidence has been pre- 

 sented to sustain this assumption, and it has been shown above, that there 

 is no source of heat present adequate to cause such fluidity. All the speci- 

 mens of a suite illustrating the manufacture, prepared under the eye of Mr. 

 Bessemer, show that such heat of fluidity is unnecessary. 



" These specimens prove that the molten mass of pure iron is not a liquid 

 iron, but a semi-fluid, composed of crystals of pure iron, which, in accord- 

 ance Avith the laws of crystallization, have withdrawn from the fluid, merely 

 wet by the fluid iron present, and rendered pultaceous by the carbonic oxide 

 gas entangled. This physical condition of the iron is represented by parti- 

 cles of hail mixed with a small proportion of water, or more exactly by the 

 mixture of crystals of sugar and concentrated syrup, as it is filled into the 

 forms; such a mass will flow and take sharp impressions in the moulds, 

 while its texture, on cooling, is highly crystalline and porous. Although the 

 iron in this state is as pure, chemically, as any bar-iron, its mechanical state 

 does not assimilate it to malleable iron, and the ingots rarely present the 

 compactness of cast-iron of the coarser qualities. A careful examination 

 of the specimens suggests the conclusion, that much of the character of 

 fluidity is also due to the presence of the engaged carbonic oxide, which, 

 like any gas disengaging from a dough-like semi-solid, causes it to flow. 



" This mechanical constitution of the pure iron removes the difficulty 

 which every iron-master must have conceived to exist in the descriptions of 

 the new method heretofore published, and it will be seen that the effects pro- 

 duced in the old and new process are strikingly similar; while the fuel in 

 the one case is iron, in the other the ordinary coke or coal. In removing 

 the iron from the furnace, the puddler depends on forming a rude porous 

 aggregate, while Mr. Bessemer, by a refined mechanical agitation, converts 

 the whole into a semi-solid, crystalline mass, full of gas-bubbles, which flows 

 from an inverted vessel, and takes the form of the moulds." 



ON THE COMPOSITION AND PREPARATION OF BRONZE POWDERS. 



Hr. Kb'nig has made some experiments, with the view of ascertaining the 

 mode of preparing bronze powder, which is generally kept secret. The 

 specimens he examined were those known commercially as 



1. Pale yellow. 2. Yellow. 3. Reddish-yellow. 4. Orange. 5. Copper- 

 red. 6. Violet. 7. Green. 8. White. 



The bronze powders, 1, 2, 3, 4, 6, and 7, were found to consist of copper 

 and zinc, with traces of iron. 3, 4, ti, and 7, contained a small amount of 

 oxidized copper, the surface of the particles being covered with suboxide of 

 copper. This is shown by the action of acids; for when the powder was 

 covered with dilute sulphuric or hydrochloric acid, the color immediately 

 disappears, owing to the solution of the thin layer of suboxide, and the 

 proper color of the alloy appears. The amount of oxygen could not be 

 estimated in any of these bronzes, but it did not amount to one thousandth. 

 The bronze powder called white, contains zinc and tin. The bronzes 3 7 

 were also found to contain a minute quantity of fat, which, on dissolving 

 the powder in dilute acid, separated upon the surface of the liquid in the 

 form of a thin film. 



