Phosphorus is found in almost all animal substances, and in some plants which give a kind of animal analysis. In all these it is usually combined with charcoal, hydrogen, and azote, forming very compound radicals, which are, for the most part, in the state of oxyds by a first degree of union with oxygen. The discovery of Mr Hassenfratz, of phosphorus being contained in charcoal, gives reason to suspect that it is more common in the vegetable kingdom than has generally been supposed: It is certain, that, by proper processes, it may be procured from every individual of some of the families of plants.
As no experiment has hitherto given reason to suspect that phosphorus is a compound body, I have arranged it with the simple or elementary substances. It takes fire at the temperature of 32° (104°) of the thermometer.
TABLE _of the Binary Combinations of Charcoal._
_Simple_ _Substances._ _Resulting Compounds._
{ Oxyd of charcoal Unknown. Oxygen { Carbonic acid Fixed air, chalky acid.
Sulphur Carburet of sulphur } Phosphorus Carburet of phosphorus } Unknown. Azote Carburet of azote }
{ Carbono-hydrous radical Hydrogen { Fixed and volatile oils
{ Of these only the carburets of Metallic substances Carburets of metals { iron and zinc are known, and { were formerly called Plumbago.
Alkalies and earths Carburet of potash, &c. Unknown.
SECT. X.--_Observations upon Charcoal, and its Combinations with Simple Substances._
As charcoal has not been hitherto decomposed, it must, in the present state of our knowledge, be considered as a simple substance. By modern experiments it appears to exist ready formed in vegetables; and I have already remarked, that, in these, it is combined with hydrogen, sometimes with azote and phosphorus, forming compound radicals, which may be changed into oxyds or acids according to their degree of oxygenation.
To obtain the charcoal contained in vegetable or animal substances, we subject them to the action of fire, at first moderate, and afterwards very strong, on purpose to drive off the last portions of water, which adhere very obstinately to the charcoal. For chemical purposes, this is usually done in retorts of stone-ware or porcellain, into which the wood, or other matter, is introduced, and then placed in a reverberatory furnace, raised gradually to its greatest heat: The heat volatilizes, or changes into gas, all the parts of the body susceptible of combining with caloric into that form, and the charcoal, being more fixed in its nature, remains in the retort combined with a little earth and some fixed salts.