Qualitative chemical analysis / by C. Remigius Fresenius.

Date:
1869
Catalogue details

Licence: Public Domain Mark

Credit: Qualitative chemical analysis / by C. Remigius Fresenius. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    By multiplying the quantity of cyanide of silver found by •2017, you will find the corresponding amount of anhydrous hydrocyanic acid. And by multiplying this again by 2—as only half the distillate was used—you will find the total quantity of hydrocyanic acid in the matter examined. Detection of Phosphorus* PEELIMINART EXAMmATION. 1. Notice whether the matter smells of phosphorus, or is luminous in the dark, taking care at the same time to bring it thoroughly into contact with the air by stirring or shaking. 2. If phosphorus has not been indicated in 1, put a little of the matter into a flask, suspend in the latter, by the aid of a loose cork, a slip of filtering paper moistened with nitrate of silver, and heat to 30° or 40°. If the paper does not turn black, even after some time, no unoxidized phosphorus is present, and it will be useless to proceed to the regular examination. If, on the other hand, the paper turns black, this is no positive proof of the presence of unoxidized phosphorus, since hydro- sulphuric acid,* formic acid, putrifying substances, &c., will produce this effect. THE REGULAE EXAMmATION. For this, one of the two following methods may be used. Method 7.t Mix the matter with water and some sulphuric acid, and distil slowly in a flask with a Liebig's condenser. If the matter contains phosphorus, a strong luminosity, usually a luminous ring, will appear in the dark in that part of the inner tube of the condenser which is first cooled. If you take for distillation 150 c.c. of a mixture containing only 1*5 mgrm. of phosphorus, and accordingly only 1 part of phosphorus in 100,000 parts, you may distil over 90 c.c.—which will take at least half an hour—without the luminosity ceasing. Mitscherlich, in one of his experiments, stopped the distillation * To ascertain whether the blackening is caused by hydrosulphuric acid, you may test with a strip of paper moistened with acetate of lead. t E. Mitscherlich, Journ. f. prakt. Chem., 66. 238.