From the experiments of Margraff and Pelletier, it seems probable that phosphorus unites both with arsenic and its oxide. By distilling a mixture of equal parts of arsenic and phosphorus in a carefully regulated heat, Pelletier obtained a residuum of a black shining substance, containing a good proportion of phosphorus. The same was obtained in the humid way, by keeping phosphorus in fusion on arsenic under water for some time. The phosphuretted oxide may be obtained by distilling phosphorus and the white oxide of arsenic together, the phosphuretted oxide sublimes mixed with arsenic and phosphorus in a separate state. It is of a red colour. The proportions in neither case were ascertained. It is probable that the compounds are of the most simple kind, or one atom to one; in that case we shall have 21 arsenic and 9⅓ phosphorus, or 100 arsenic and 44 phosphorus for phosphuret of arsenic; and 28 oxide and 9⅓ phosphorus, or 100 oxide and 33 phosphorus for phosphuretted oxide. No precipitation is occasioned by phosphuretted hydrogen water in solutions of arsenic. 23. _Phosphuret of cobalt._ Cobalt unites with phosphorus in the direct way as well as by being heated with phosphoric glass. The colour of the compound is a blueish white; it is brittle and crystalline in the fracture. The metal acquires 7 per cent.; this is below the theoretic quantity, which is 25 per cent. if the atom of cobalt be 37. Solutions of cobalt give no precipitate by phosphuretted hydrogen water. 24. _Phosphuret of manganese._ This compound may be formed like the preceding ones. It is of a white colour, brittle and of a granular texture. It is not liable to be altered by the air like the pure metal. The proportions of the compound Pelletier did not determine. Reasoning from theory, it should consist of 25 metal and 9⅓ phosphorus; or 100 metal and 37 phosphorus. The salts and oxide of manganese are not sensibly affected by phosphuretted hydrogen water. * * * * * The combinations of the remaining metals with phosphorus can scarcely be said to have been investigated. SECTION 16. CARBURETS.