Volume 1
A treatise on chemistry / by H.E. Roscoe and C. Schorlemmer.
- Henry Enfield Roscoe
- Date:
- 1877-1892
Licence: Public Domain Mark
Credit: A treatise on chemistry / by H.E. Roscoe and C. Schorlemmer. Source: Wellcome Collection.
522/792 page 506
![addition of a drop of the solution to a drop of a solution of ferro- cyanide of potassium with which the slightest excess of uranium acetate produces a brown colour. Metaphosphates and pyrophosphates must first he converted . into orthophosphates before precipitation. In like manner phosphorus itself as well as the hypopliosphites and phosphites may also be quantitatively determined in the form of phosphoric acid by previously oxidizing them with nitric acid. Chlorides and Bromides of Phosphoric Acid. The hydroxyl groups contained in the three modifications of phosphoric acid may be replaced as is the case with other oxi- acids, by chlorine or bromine thus giving rise to the oxychlorides and oxybromides of phosphorus, as they are commonly termed. Phosphorus Oxychloride or Piiosphoryl Chloride. POCl3. Vapour density = 7G'46. 304 This compound was discovered in the year 1847 by Wurtz,1 who obtained it by decomposing the pentachloride with the requisite quantity of water: PC15 + I120 = POCI3 + 2HC1. The best method of preparing this substance is the one pro- posed by Gerliardt f namely, by heating dried oxalic acid with phosphorus pentachloride when the following reaction takes place :— PC16 + H2c204 = POCl3 + 2HC1 + C02 + CO. Instead of oxalic acid, boracic acid may be employed, thus:— 3PC15 + 2B(OH)3 = 3P0C13 + B203 + 6HC1. Pure phosphorus oxychloride may also be easily obtained by heating the pentachloride and the pentoxide together in sealed tubes in the proportion of 3 molecules of the former to one molecule of the latter :3 3PC16 + P205 = 5P0C13. A nn. Chim. Phya. [3] xx. 472. 2 Ann. Chim. Phys. [3] xliv. 102. 3 Gerliardt and Chiozza, Ann, Chcm. Pharm. lxxxvii. 290. 1](https://iiif.wellcomecollection.org/image/b28122409_0001_0524.jp2/full/800%2C/0/default.jpg)
