BULLETIN OF THE BUSSEY INSTITUTION. 201 
Rose,* who proved by numerous experiments that charcoal, prepared 
even at low temperatures, from vegetable and animal matters, rich in 
phosphorus, always retains a certain amount of a phosphorus compound 
that is insoluble in acids. We are ignorant as to the precise character of 
the insoluble compound or compounds thus left with the charcoal. None 
of them have ever been isolated.. But in the case of wood-ashes, such as 
haye here been examined, there are grounds for believing that a part at 
least of the insoluble matter may be phosphide of iron, or some other 
metallic phosphide. 
There are many instances on record of the ease with which phosphates 
are reduced to phosphides under conditions such as are probably to be 
- found in some parts of almost every domestic fire where the ashes are 
strongly heated in contact with the particles of carbon with which they 
are admixed, or in an atmosphere of carbonic oxide or of carburetted 
hydrogen. One of the commonest methods employed by chemists for 
preparing metallic phosphides, is to ignite a quantity of the metal or of 
its oxide with a mixture of bone-black, quartz-sand, and charcoal, either 
with or without an alkaline flux.+ Phosphide of iron, in particular, may 
be readily prepared, after Berzelius, by igniting a mixture of phosphate of 
iron and lamp-black, or some other form of carbon. It is a fact well known 
to metallurgists, that iron and phosphorus combine with one another with 
special ease to form a very stable phosphide. When iron-ores that are 
contaminated with phosphates are smelted, all, or nearly all, the phos- 
phorus that was contained in them, as well as that contained in the fuel, 
is found in the iron, in the form of a phosphide.t{ 
I have myself noticed that very considerable amounts of impure phos- 
phide of iron may be produced by igniting in a platinum crucible the 
mixed precipitate of basic acetate and phosphate of iron, that is obtained 
in the ordinary analytical process of precipitating phosphoric acid by means 
of a ferric salt in presence of free acetic acid. In employing this method of 
analysis, it is in fact an essential requisite to success that the mixed precip- 
itate of ferric phosphate and acetate shall not be ignited directly. The 
precipitate must be dissolved in acid, after it has been washed, and be 
reprecipitated as simple phosphate before it can be ignited and weighed. 
In case phosphide of iron has once been formed within the mass by ignit- 
ing it in contact with the ferric acetate, it is idle to attempt to oxidize the 
phosphide, either by long-continued ignition of the precipitate in the air, 
or by repeatedly drenching it with nitric acid. The inertness and persis- 
tence of the impure phosphide of iron formed under these conditions are 
remarkable. It resists the action of strong acids, like the phosphide de- 
* Poggendorft’s ‘‘ Annalen,” 1847, 70. 449; 1849, 76. 305; 1850. '79. 398; 
80. 94. ' 
t Compare Berthier, “ Traité des Essais par la Voie Séche,” 1. 567, and 
Gmelin’s ‘‘ Handbook of Chemistry,” 5. 222. 
t Compare Wagner’s “ Jahresbericht,” 6. 82 and 9. 40. 
wiike x. 26 
