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.
558/792 page 542
![satisfactory was known concerning the chemical nature of this salt for a long time. Homberg1 first prepared boric acid from borax in the year 1702, and he termed it sal sedativum, for he was unacquainted with the composition of the acid. It was not till 1747-8 that Baron showed in two memoirs read before the French Academy that borax was a compound of sal sedativum and soda. After the establishment of the Lavoisierian system, the name boracic acid was given to sal sedativum, and it was then assumed that this acid contained an unknown element, for the isolation of which we are indebted to Gay-Lussac and Thenard,2 as well as to Sir Humphry Davy,3 who about the year 1808 obtained elementary boron. Boron occurs in two allotropic modifications : amorphous and crystallized. Amorphous Boron.—This modification was obtained by Gay- Lussac by heating boron trioxide, B203 (obtained by the ignition of boric acid), with potassium in an iron tube. It is also obtained by mixing ten parts of coarsely-powdered boron trioxide with six parts of sodium, and bringing the mixture into a crucible already heated to redness, and covered with a layer of powdered chloride of sodium previously well dried. As soon as the reaction, which is very violent, lias subsided, the mass is stirred with an iron rod until all the sodium has been oxidized, and then carefully poured into water acidified with hydrochloric acid. The soluble salts dissolve in the water, whilst the boron re- mains behind as an insoluble brown powder. This is then collected on a filter, and it must be very carefully dried, as it is easily oxidized and may take fire. Amorphous boron is a dark brown powder which does not possess either smell or taste. It does not undergo any alter- ation in the air or in oxygen; nor does it melt even at a white heat, but may be fused when heated in the electric arc of 600 Bunsen elements. It is a non-conductor of electricity, and when freshly prepared and not strongly ignited is slightly soluble in water, imparting to it a yellow colour and being precipitated unchanged from its aqueous solution on the addition of acids or salts. Crystallized or Adamantine Boron.—This substance was first obtained in the year 1856 by Wohler and Deville.4 It can be ] Crell. Charn. Archiv., ii. 265. 2 JRecherches, i. 269. 3 Decomposition of boracic aeH, Phil. Tram. 1S09 i. 75. 4 Ann. Chcrn. Pharm. ci. 113.](https://iiif.wellcomecollection.org/image/b28122409_0001_0560.jp2/full/800%2C/0/default.jpg)
