OXALATES, NITRATES, PHOSPHATES, SULPHATES, AND CHLORIDES. 
65 
The view expressed above in the formula is much more likely to be true, namely, that 
this salt is simply a tribasic phosphate, of which the three atoms of base are all dif- 
ferent : they are soda, oxide of ammonium, and water ; and the salt possesses eight 
atoms of water of crystallization. By a graduated heat it is possible to expel the 
water of crystallization of this salt, and likewise the ammonia of its oxide of ammo- 
nium ; and the water of the last remaining as base, the salt Na H 2 P is produced. 
M. Mitscherlich now admits that there is no tribasic phosphate corresponding 
with this, but containing potash instead of oxide of ammonium, a conclusion of which 
I have ascertained the accuracy. 
I endeavoured to form a tribasic phosphate to contain two atoms soda and one 
atom of oxide of ammonium, but such a salt appears to have no existence. For when 
ammoniacal gas was passed into a strong and hot solution of the common phosphate 
of soda, a slight deposition of the tribasic phosphate of soda took place, followed by 
the rhomboid.al crystals of the common phosphate unchanged. 
It likewise appears that when the bibasic phosphate of soda and the bi basic phos- 
phate of potash (pyrophosphates) are mixed together, no new salt is produced ; but 
the former may be crystallized out, and the latter remains uncrystallizable. 
II. Tribasic Phosphates containing Oxides of the Magnesian Class . 
1. Tribasic Phosphate of Zinc and Water. ( Phosphate of Zinc.) 
Zn 2 H P + 2 H. 
This salt, which is nearly insoluble, is obtained in minute silvery plates, by mixing 
three ounces of sulphate of magnesia with four ounces of phosphate of soda, each 
dissolved in two pounds of cold water. These crystalline plates consist of 
Theory of Zn H P + 2 H. 
Anhydrous salt . . . 100 ” 100 * 
Water ..... 19-63 17*77 
119-63 117-77 
Dried above the melting point of tin the crystals still retained a glistening appear- 
ance, but had lost two thirds of their water ; for they now consisted of 
Theory of Zn H P. 
Anhydrous salt . . . 100 - 100 - 
Water ..... 6-08 5-92 
106-08 105-92 
The two atoms of water which are expelled in the above experiment are, notwith- 
standing, pretty strongly attached to the salt, being retained at the boiling point of 
water. Indeed these two atoms of water are highly constitutional, and are found in 
all the phosphates of this class. 
mdcccxxxvii. k 
