276. Applicability of the Process.—Experience has shown that sulfuric acid is the only substance which need be removed from ordinary fertilizers preparatory to the estimation of the potash by means of perchloric acid. The fact that this process can be used in the presence of phosphoric acid is a matter of great importance in the estimation of potash in fertilizers, inasmuch as these fertilizers nearly always contain that acid. The fact that the French chemists noticed that magnesia was a disturbing element in the process, as has been indicated in volume first, probably arose from its presence as sulfate. Neither Caspari nor Kreider has noticed any disturbance in the results which can be traced to the presence of magnesia as a base.
If ammonia be present, however, there is a tendency to the production of ammonium perchlorate which is somewhat insoluble in the alcohol wash used. Solutions therefore containing ammonia before treating by the perchlorate method for potash should be rendered alkaline by soda-lye and boiled. With the precautions above mentioned, the method promises to prove of great value in agricultural analysis, effecting both a saving of time and expense in potash determinations.
277. Accuracy of the Process.—The perchlorate was tried in conjunction with the platinum method on the two samples of potash fertilizer prepared and distributed by the official reporter on potash for 1893.[238] One of the samples was of a fertilizer which had been compounded for the Florida trade and contained bone, dried blood, and potash, mostly in the form of sulfate. The other sample consisted of mixed potash salts, sulfate, chlorid, double salt, kainit, and about five per cent of the triple sulfate of calcium, potassium, and magnesium.
The results obtained by Wagner and Caspari on the two samples follow:
| Sample No. 1. Per cent potash. | Sample No. 2. Per cent potash. | |
|---|---|---|
| By the platinum method | 13.25 | 37.98 |
| By the perchlorate method | 13.09 | 37.82 |
The perchlorate method on the whole appears to be quite as accurate as the platinum process, requires less manipulation and can be completed in a shorter time and at less expense for reagents.
AUTHORITIES CITED IN
PART THIRD.
[185] Connecticut Agricultural Experiment Station, Bulletin No. 97, p. 7.
[186] Annual Report Connecticut Station, 1892, p. 32.
[187] Colorado Agricultural Experiment Station, Bulletin No. 10.