﻿Skey. — On the Alkalinity or Acidity of certain Salts atid Minerals. 325 



this criticism, but I waited in tlie hopes that some one might have taken up 

 the question with such authority and potency of argument as would have 

 settled it one way or the other, and thus saved me further thought on this 

 subject, as it is so much more pleasant and exhilarating, besides being more in 

 accordance with our colonial instincts, to break up fresh ground or explore 

 new country, than to turn back from this to tinkering about old work, or to 

 protect it from hostile blasts, even though these be ever so courteously blown 

 or kindly tempered. 



I will only add that I shall be very glad to have the subject still further dis- 

 cussed, especially as it now appears likely that some general principle may soon 

 be recognised, by the use of which we can easily and certainly classify into the 

 three distinctive groups, acidic, basic, and neutral, those bodies whose re-action 

 with test paper is difficult to observe by reason of their intense colour or their 

 extreme insolubility in water. 



Art. — LYI. — On the Alkalinity or Acidity of certain Salts and Minerals, as 

 indicated hy their Reaction loith Test Paper. By W. Skey, Analyst to 

 the Geological Survey of New Zealand. 



\Read before the Wellington Philosophical Society, 28th October, 1871.] 



A KNovfLEDGE of the reaction of various substances with test paper is justly 

 esteemed of considerable importance, since it enables us at once to refer them 

 to one or other of three distinctive gi^oups, each of which has strict regard to 

 the molecular structure of those substances falling within it, as manifested by 

 the chemical combinations they are most prone to form. These groups are, as 

 is well known, the alkaline or basic, the acidic, and the neutral, and properly 

 prepared test paper indicates the one to which any particular substance belongs 

 by suffering certain colourations when brought in contact with it, these 

 changes being the result of chemical ones, by which the combinations previously 

 existing among the colouring matter of such paper are ruptured, and new ones 

 superinduced. 



The terms alkalinity and acidity, therefore, have a signification expressive 

 of condition, and their real meaning is only this, that as applied to any sub- 

 stance they indicate a tendency in such to form combinations with acid or 

 alkaline bodies, as the case may be. Neutrality, however, has a relation more 

 to the breaking point (if I may so term it) of these combinations in the litmus 

 paper, than to absolute condition of the substance tested ; for it is easy to 

 conceive that a substance may be acid or alkaline, and still, by reason of the 

 feebleness of either these characters, be unable to overturn the combinations 

 referred to, and so manifest either of these reactions. 



s s 



