OXALATES, NITRATES, PHOSPHATES, SULPHATES, AND CHLORIDES. 51 
decomposition, left 10' 14 grains of carbonate of potash. Allowing the potash an 
equivalent proportion of oxalic acid, the salt must consist by this experiment of 
Potash 32'23 
Oxalic acid . . . 49'38 
Water 18'39 
100* 
The water almost coincides with three atoms, which would amount to 18'42 per cent, 
of the salt. 
In the formation of the binoxalate of potash, the constitutional atom of water of 
the neutral oxalate of potash appears to be displaced by an atom of hydrated oxalic 
acid ; so that the formula of binoxalate of potash represents anhydrous oxalate of 
potash, followed by oxalate of water with two atoms of water, as given above. The 
same principle of derivation applies most happily to that anomalous salt, the qua- 
droxalate of potash, 
8. Quadroxalate of Potash. 
Analytic formula . . . K (CC) 4 IT 7 . 
Rational formula . . . K CC + H CC -j- 2 (IT CC IT 2 ). 
The formula of the preceding salt is terminated by two atoms of water : let us re- 
place them by two atoms of hydrated oxalic acid, and we have the quadroxalate of 
potash. We thus derive the quadroxalate from the binoxalate, in the same way that 
the binoxalate itself is derived from the oxalate. 
There can be no doubt, from the accurate analysis of Berzelius, that this salt 
contains seven atoms of water. He found 100 parts of the quadroxalate of potash to 
yield by ignition 27'225 carbonate of potash. In an experiment in which 1 7*3 grains 
of the salt were ignited by us, there resulted 4*7 carbonate of potash ; which is 27'11 
carbonate of potash from 100 quadroxalate. Berzelius determined the water directly 
by igniting the salt with oxide of copper, and found it to amount to 24'8 per cent, of 
the salt. Calculated from our experiment, the water comes out 25'05 per cent., while 
the theory of seven atoms of water in the salt requires 24'72 per cent. 
1Q'87 grains of this salt, dried by a nitre-bath, of which the temperature was 240°, 
lost eventually 1'46 grains; or 100 salt lost 13'43. Four atoms of water amount to 
14T2 per cent, of the salt, to which the experimental result approximates sufficiently 
to prove that this salt parts readily with four of its seven atoms of water. These four 
atoms of water are evidently the constitutional water of the two atoms of hydrated 
oxalic acid, which the quadroxalate contains. When the salt is still more strongly 
heated, oxalic acid itself goes off, partly as a sublimate and partly in a decomposed 
state. 
