64 
PROFESSOR GRAHAM ON THE CONSTITUTION OF 
first in the name that base of which two atoms are present. Thus the bi phosphate 
of soda is “ the phosphate of water and soda,” and the phosphate of soda is the phos- 
phate of soda and water, both being- at the same time characterized as “ tribasic.” 
What I have to add at present in regard to the phosphates relates chiefly to the 
last three salts, of which formulae are given in the preceding Table, which belong to 
classes of tribasic phosphates that were not examined in my former paper upon the 
phosphates*. But I may premise a few observations, which are more strictly supple- 
mentary to the results of that paper. 
1 . The bibasic phosphate of water (pyrophosphate of water) is possessed of very 
considerable stability. Both weak and concentrated solutions of this salt have been 
kept for five or six months without any sensible change or production of the tribasic 
phosphate of water. 
2. It appears to be impossible to crystallize any bibasic phosphate (pyrophosphate) 
of potash. Such salts can exist in solution, but not in the dry state. The same ob- 
servation applies to the bibasic phosphates of ammonia, or we have no pyrophosphates 
of ammonia except in solution. Indeed, the solution of the bibasic phosphate of water 
and ammonia assumes another atom of basic water when the evaporation is carried 
far, and crystallizes as the tribasic phosphate of water and ammonia (biphosphate of 
ammonia). 
3. In the case of tribasic phosphates containing potash, I have succeeded in cry- 
stallizing the tribasic phosphate of potash, and the tribasic phosphate of water and 
potash, but not the tribasic phosphate of potash and water, or what would be con- 
sidered on the old view as the neutral phosphate of potash. 
4. Both the bibasic and tribasic phosphates of water maybe treated with an excess 
of caustic potash in solution without the formation of any precipitate or sparingly 
soluble combination. It is only in the monobasic phosphate of water that a 
sparingly soluble combination is formed by potash, such as that which is described 
by Dr. Thomson under the name of diphosphate of potash. 
I. Tribasic Phosphate of Soda, Ammonia, and Water. {Phosphate of Soda and Am- 
monia : Microcosmic Salt.) 
NaNH I. * * 4 H P + 8 H. 
I have repeated more than once the analysis of this salt, and obtained the same 
result as M. Mitscherlich. It appeared to contain 0-5094 of volatile matter: and 
there may be derived from an atom of this salt one atom of phosphoric acid, of soda 
and of ammonia respectively, and ten atoms of water. It has hitherto been viewed 
as a double phosphate or combination of phosphate of soda with phosphate of am- 
monia ; but no reason can be assigned why these particular salts should combine 
together, and combinations of salts of soda and ammonia are exceedingly unusual. 
* Philosophical Transactions, 1833. 
