Mr. W. A. Dixon on the Constitution of Acids. 129 



7 00H 

 Hypophosphorous acid is P— H , and is therefore mono- 

 basic. H 

 Pyrophosphoric acid is probably 



/OOH 

 P\OOH 

 IvOOH' 



^OH 



as the dipotassic and disodic salts are acid in reaction, whilst 

 the dipotassic ammonium hydrogen salt is alkaline, showing 

 the feeble acidity of the OH group; and a tripotassic or tri- 

 sodic pyrophosphate should also be alkaline. 



Orthosilicic acid is usually supposed to be tetrabasic, and 

 could then have only four lrvdroxyl atoms and no oxyhydroxyl, 

 and should therefore possess scarcely acid properties. The 

 acid obtained by diffusion when perfectly free from chlorine 

 has a very faint acid reaction ; but as this solution evaporated 

 in vacuo leaves a residue having the composition H 2 Si0 3 , the 

 acid in solution may be 



/OOH 



Si/° H ' 

 ° N OOH 



and hence give an acid reaction. 



Of the sulphur acids we have sulphuric, ^Kqq tt, and 



sulphurous, S^qH , the first forming acid and the second 



alkaline hydrogen salts with the alkaline metals. There is also 



hyposulphurous acid, S<(jj , which should be monobasic, 



and actually only forms one sodium salt. The substitution of 

 sulphur for oxygen in sulphuric acid renders this sulphuric 

 acid too unstable to form acid salts with the alkali metals. 

 There are some monobasic acids, as nitric, metaphosphoric, 

 and chloric, which may have the same or different constitu- 

 tions. They may be 



v/OOH p/OOH pl /OOH 

 1N ^0 ' r ^O ' O1 ^0 ' 



N OH P OH CI OH 

 or ' ■ y\ /\ /\ 



0-0 ' 0-0 * 0-0 



Chloric acid may have the latter constitution ; but it seems 

 most probable that nitric acid, from its strongly acid character, 

 Phil Mag. S. 5. Vol. 21. No. 129. Feb. 1886. K 



