ON CHEMICAL NOMENCLATURE. 



45 



we find the tevms hijponUric acid and peroxide nf nifroncn applied to the 

 fonrth oxide, the other oxides being called nitrous and nitric oxides, nitrous 

 and nitric acids. 



In the earlii3r edition of Fownes' * Manual,' the terras protoxide and 

 binoxide of nitrogen are applied to the lower oxides, nitrons acid to the 

 third, hyponitric and nitric acids to the fourth and fifth. In the tenth 

 edition the terms nih-aijfa inoiui.vitk' and dioxide are adopted for the two 

 lower and tctroxide for the fourth oxide; the terras nitrous oxide and nitro- 

 gen trioxide are given to the third, and the terms nitric oxide and nitrogen 

 pentoxide to the fifth. The terms nitrous and nitric oxides here applied 

 to the fourth and fifth oxides had previously only been applied by chemists 

 to the first and second. 



TABLES III. V. 



The older chemists were agreed in designating the two oxides of 

 sulphur the unlplinrov}^ and tlie ,->idplinric acids respoct^'vely. In Fownes' 

 'Manual,' ed. 18G.'), the alterrative names sulphur di- and triti.iu'de are first 

 introduced, whic^h, among the later writers, have gradually superseded 

 the former Jiaraes. 



In a memoir in the ' Jahresberitht,' 1842, BcTzelius recommends the 

 introduction of the names Di-, Tri- and Tt'trathionic acids. This nomen- 

 clature has superseded the older names hyposulphuric, monosulphyposul- 

 phuric, itc, acids, though some few of the later writers rjtain the term 

 hyposulphuric acid. 



The discovery of the true hi/pnsulphurous acid by Schiiizenberger 

 caused the acid, hitherto known by that name, to be designated tJiiosul- 

 l^hurir acid, as derived from sulphuric acid, by the replacement of one 

 atom or oxygen by sulphur. Ilydrosulphurous acid, the name originally 

 proposed by Schiitzenberger for his acid, seeras to be retained only by the 

 French writers. 



Is oxide 

 nitro- 

 many 

 jysteni 

 led ; in 

 He and 

 fourth 

 Kis acid 

 liomen- 

 litreux, 

 Ind the 

 :1842) 



TABLES VI.-VII. 



The oxides of chromium afl'ord an instance of change of names owing 

 to the discovery of another member of a series of compounds. Thus the 

 green oxide of chromium was designated the protoxide, until the isolation 

 of an oxide cotitaining one atom of oxygen to one of the metal. The 

 latter compound was then called the protoxide, while the name of the 

 former was altered to scsqitioxidr. 



The potassium and lead salts of chromic acid afford a good example 

 of the want of imamimity of nomenclature among the older writers in 

 those ca.ses in which there are derived from one acid two salts, the one 

 neutral, containing one equivalent of basic to one equivalent of acid oxide, 

 tlie others containing an excess of either of the oxides. Thus the acid or 

 rod potassium chroniate is called indifi'erently potassium di or /u'chromate, 

 but the former prefix is equally applied to the basic lead chromate. The 

 later writers have avoided this confusion of prefixes by introducing the 

 di or /// before the name of the acid or metal according as the salt con- 

 tains excess of the acid or the basic oxide, respectively, thus ; — ■ 



Potassium (?/chroraate, but (//plumbic chromate. 



