200 Progress of Foreign Science. 
phosphate of soda. Berzelius calls the salts which are in this 
degree of saturation, neutral phosphates and arseniates, a deno- 
\mination retained by M. Mitscherlich. If we precipitate a solution 
of muriate of barytes by a phosphate or arseniate, taking care 
to add the solution drop by drop, the liquor which remains 
after the complete precipitation of the acid shews then a neutral 
re-action, and yields no cloud withammonia. The arseniate 
and the phosphate of barytes which have been precipitated are, 
by analysis, found to be in the same degree of saturation as the 
above-mentioned salts. The oxide of lead comports itself in 
the same way as barytes. 
If we add to the above salts as much acid as they previously 
contained, we obtain bi-phosphates, and bin-arseniates of pot- 
ash, soda, and ammonia, in which the oxygen of the base is to 
the oxygen of the acid as 1 to 5. On adding to a solution of 
a neutral salt, with base of barytes, these bi-phosphates or 
bin-arseniates, no precipitate takes place; for the bi-phosphate 
and bin-arseniate of barytes are soluble in water. We obtain 
these two salts, if we dissolve the neutral arseniate or phosphate 
of barytes in phosphoric or arsenic acid, and set the solution to 
crystallize. The bi-phosphates contain, according to Berzelius, 
exactly a double quantity of acid to that in the neutral salt. 
If we precipitate the solution of a neutral salt, having for base 
lime, zinc, copper, silver, mercury, or several. other oxides, by 
a neutral arseniate or phosphate, the liquor shews, after the 
precipitation, a very acid re-action, and we must add much 
ammonia to neutralize it. The oxygen of the base is to that of 
the acid in these precipitated salts as 3 to 5. A solution of a 
neutral arseniate or phosphate shews always alkaline to the 
usual tests. To a solution of an arseniate and phosphate of 
soda, in known quantity, sulphuric acid was added, till the 
solution appeared to be neutral; a point, however, very diffi- 
cult to hit, for if litmus paper shew an acid predominance, 
that stained with turmeric or rhubarb indicates excess of alkali. 
After adding to this liquor much muriatic acid, it was preci- 
pitated by muriate of barytes; and from the sulphate of this 
earth which was obtained, the quantity of sulphuric acid em- 
ployed to render the solution neutral, was computed. It thus 
appeared that the acid added to neutralize a solution of a 
crystallized phosphate or arseniate, saturates the third of the 
base. 
If we add to a phosphate or arseniate, phosphoric, or arsenic 
acid, as long as it shews a neutral re-action, and if we precipitate 
muriate of barytes, by this solution, we obtain a precipitate 
which is a neutral salt, with base of barytes; but the solution 
shews powerfully acid to tests, and yields, when treated with 
ammonia, an abundant precipitate, because a bi-phosphate or 
bin-arseniate of barytes was formed. The degree of saturation 
