ON ClIEMlCAIi NOMENCLATDRK. 



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Tho employment of sncli terms as ' Phosphorsupercbloriir,' 'intcr- 

 mediiirei" Chlorphosphor ' for the trichloride, and tho corresponding 

 ' I'hosphorsuperchlorid,* ' Chlorphosphorsepim maximum ' for the penta- 

 chloride, is explained by the fact that a solution of phosphorus in the 

 trichloride was formerly supposed to be a lower chloride of phosphorus, 

 ' Phosphorchloriir,' ' Chlorphosphor im minimum.* 



The followinfj: observations relate to the prevalence of certain names at 

 different periods : — 



1. Anhydrous Pli(is))hiirovs Acid was formerly called phosphorous acid ; it 

 is now usually culled phosphorous anhydride, and to a le^■s extent phos- 

 phorus trioxido. 



2. Hydric FlinKpJiUe was called (v.hen obtained from tricbloride of 

 phosphorus and water) a compound of phosphorous acid and water. 

 From 1810 till 18(Ji) it was called hydraio of phosphorous acid or hydrated 

 phosphorous acid. It is now called pho.'^jjliorous acid. The term hydric 

 phosphite has been very seldom used. 



.'!. Anhydrous Vhns)diiiric Arid was originally called pjiosphoric acid ; it 

 is now usually called ])liospliotic anhydride, and to a less extent phos- 

 phorus pentoxide. The teini anhydrous phosphoric acid has been fre- 

 fpiently employed. 



4. Hydric I'hosphalc was called hydrate of phosphoric acid or hydrated 

 pbosphoric acid till 18G() ; it is now called phosphoric acid. The term 

 iiydiic phosphate has been seldom used. 



5. Trichloride of Phofiphnrus. — The terras protochloride of phosphorus 

 and phosphorous chloride (or Phosphorcloriir) were of equal prevalence 

 till 18G8, when the former expired. Trichloride of plios[)horus is tho 

 name now chiefly used. 



G. Similar remarks apply to pnitachhrridr of phonphoras, except that tho 

 term porchloride of phosphorus has been more largely used than plios- 

 phoric chloride, although it expired in 18G8, 



TABIiE Xr. 



In this table we find that the names 'chloride of copper,' 'dichloride 

 of copper,' and ' protochloride of copper," have all been applied to tho 

 lower chloride, and the names ' chloride of copper,' ' deutochloride,' 

 ' bit^hloridc,' and ' protochloride of copper,' have all been applied to the 

 higher ehloiide. Th. Thomson int' oduced the names proto- and deuto- 

 chloride for the 1st and Stid chloride respectively, but later on ho adopted 

 the names snbchloride and chloride. Brande, in the iirst edition of his 

 ' Chemistry,' calls the two bodies chloride and bichloride of copper, but 

 in liis Gth edition wo find the names dichloride and protochloride, signify- 

 ing that the first has two atoms of copper and the second one. Some 

 chemists have followed this rule, others the system of Thomson, so that 

 while Brande, Watts, Rognault, and Bernays apply the name protochloride 

 to the higher body, Thomson, Thenard, Gay-Lussac, Naquet, and Har- 

 court apply the same name to the lower body. 



Oenkrai- Ri;m.\i:ks ox tui: Pim:limi\,vry Rki'Ort. 



The usefulness of any system of nomenclature rests mainly on its 

 permanence. 



Tho tables in this Report, summarising the history of the nomcn- 

 clature of certain typical chemical com[)ounds, clearly indicate tho 

 conditions most essential for permanence. Names have been given to 

 bodies expressing particnlar opinions on their ultimate constitution, whilst 

 other names have been given expressing no theoretiivil views, but simply 



