Under like conditions arsenates only give a precipitate on long-continued boiling.
The salts of arsenic acid, termed arsenates, are isomorphous with the phosphates, and in general character and reactions resemble the phosphates very closely; thus both series of salts give similar precipitates with "magnesia mixture" and with ammonium molybdate solution, but they can be distinguished by their behaviour with silver nitrate solution, arsenates giving a reddish-brown precipitate,whilst phosphates give a yellow precipitate.
In a pill), a mixture of ferrous and ferric arsenates with some iron oxide, is of great use in certain cases.
Ferri arsenas, iron arsenate, ferrous and ferric arsenates with some iron oxides, a greenish powder.
Copper arsenate is similar to cupric phosphate, and the resemblance is to be observed in the naturally occurring copper arsenates, which are generally isomorphous with the corresponding phosphates.