Analyses of the Ashes of Plants. 
cipitatctl by acetate of ammonia. The following experiments are 
selected from many others as showing that the composition of the 
phosphate is greatly dependent on the relative quantities of the 
different re-agents employed in its production. In the first two 
experiments clean iron wire was dissolved in nitro-hydrochloric 
acid; the solution was diluted with water, and phosphate of soda 
added in excess; the phosphate of iron was then precipitated 
from the acid liquid by excess of acetate of ammonia ; the pre- 
cipitate was burnt and weighed. No care was taken to use equal 
quantities of the different re-agents in the two experiments, and 
they were consequently unlike in this respect. 
Grains of Grains of Per cent, of 
Iron. Pliosphate. Peroxide of Iron. 
1st exp. 1-14 gave 3-07 = 53-09 
2nd „ 1-35 ,, 3-99 = 48-38 
In this case, then, the results are by no means uniform. 
In the two following experiments the same quantity of iron was 
dissolved — equal quantities of acid, of phosphate of soda, and 
acetate of ammonia being employed in both cases : — 
Grains of Grains of Per cent, of 
Iron. Pliospliate. Peroxide of Iron. 
1st exp. 0-75 gave 2-15 = 49-7-2 
2nd,, 0-75 ,, 2-17 = 49-30 
Here the results are nearly identical. 
Two other experiments in which the quantities of the different 
substances employed were alike, although different from those in 
the last experiments, gave the following results : — 
Grains of Grains of Per cent, of 
Iron. Phospliate. Peroxide of Iron. 
1st exp. 0-94 gave 3-08 = 43-50 
2nd „ 0-94 2-99 = 44-81 
These two results, although not perfectly identical, are sufficiently 
so to prove that the composition of phosphate of iron as precipi- 
tated by acetate of ammonia from an acid solution in the presence 
of an excess of an alkaline phosphate, is entirely decided by the 
accidental relation of the different substances present ; for it will 
be seen that whilst the percentage of oxide of iron is the same 
under the same circumstances, it is at once altered when these 
are dissimilar. 
The practical bearing of this circumstance in the analysis of 
plant-ashes is not great, since the quantity of iron present is 
generally too insignificant to alter in any material respect the 
proportion of phosphoric acid so obtained. In all cases, how- 
ever, where much iron is present it is necessary to convert the 
phosphate of iron into phosphate of magnesia by the process of 
