Progress of Invention. 231 



Sterrometal. — This important alloy possesses some valuable 

 properties which make it well deserving of attention. It may, in 

 many cases, he substituted for bronze, iron, or steel, with great 

 advantage : and is likely to prove valuable to the makers of various 

 kinds of instruments and machinery. It is formed by fusing 

 together from 55 to 57 per cent, copper, from 40 to 42 per cent, 

 zinc, 1*8 per cent, iron, and from 0*15 to 0*8 per cent. tin. The 

 colour of this compound is very similar to that of gold. The cast 

 metal is rendered malleable and ductile by hammering or pressure, 

 at a red heat — a higher heat would produce brittleness, and a lower 

 would injure the texture. The tenacity of the cast metal is equal 

 to the support of 42 "29 kilogrammes the square millimetre ; of the 

 malleable, to the support of 53*99 kilos.; and of the ductile, to the 

 support of 59*72 kilos. It takes a fine polish. 



Black Phosphorus. — Hitherto we have been accustomed to 

 consider white as the colour of perfectly pure phosphorus, or red 

 when the phosphorus is in the amorphous state. There is now, 

 however, good reason to believe that its normal colour is black. 

 Long ago, Thenard obtained black phosphorus ; but the process he 

 used was more or less uncertain, and it was never repeated with 

 success by other chemists. M. Blondlot has, however, discovered 

 an infallible process for obtaining black phosphorus. He purifies 

 phosphorus of the ordinary kind by repeated distillations, in a 

 sand-bath and in a current of hydrogen ; the yellow or impure 

 portion, which is volatile — and therefore not separable by dis- 

 tillation — being changed into red amorphous phosphorus, which 

 is fixed, by exposure for several days to .insolation, previous to 

 each repetition of the process of distillation, and the produet being 

 received into distilled water, kept at 90° Cent. When the phos- 

 phorus is become thoroughly pure, if slowly cooled, it will on falling 

 to 42° be a white mass, which, when 8° or 10° are reached, suddenly 

 changes to black. Black phosphorus becomes colourless again by 

 fusion, but recovers its blackness if slowly — and sometimes if sud- 

 denly — cooled. It is like common phosphorus, except that it is 

 more stable, softer, and more flexible. It becomes coated with 

 white, in water ; and with red, in the atmosphere : but a single 

 distillation renders it, in each case, again black. Very old phos- 

 phorus—it is supposed by some kind of spontaneous purification, 

 depending on a change in its molecular condition — is very often 

 changed to black throughout its whole mass, except the outside, 

 which is red. 



Miscellaneous. — Alloys of Manganese. — An alloy consisting 

 either of two atoms of manganese and one of iron, or of four of 

 manganese and one of iron, is harder than the hardest steel, is of a 

 colour between that of steel and silver, and is capable of receiving 

 a high polish. It fuses easily, and is not oxidizable by the atmos- 

 phere. It may be formed by keeping a mixture consisting of oxide 

 of manganese, powdered charcoal, and cast or wrought iron in a 

 state of tolerably minute division, at a white heat, for some time 

 in a graphite crucible ; the whole having been covered up in the 

 crucible by a layer of common salt, or of some other substance 



