﻿Skey. — On the Alkalinity or Acidity of certain Salts o,nd Minerals. 327 



rained by the strength of the acid employed ; a strong one being tlius neces- 

 sary, as it were, to di-aw out its highest capabilities in this respect. 



Our recently acquired knowledge of the mobility (if I may tei'm it so) of 

 the component molecules of bodies in respect to each other, even in the case of 

 simple elements, and the great tendency many of them manifest to form inter- 

 combinations among themselves, dispose us favourably towards a belief which, 

 by ascribing a variable potentiality of this nature to these bodies, explains 

 away the apparent anomaly I have just referred to as pertaining to them in 

 their pi'esent reputed condition, and make it very desirable to have experi- 

 mental results, by which to enable us to decide between theory and our present 

 belief Results, therefore, having for their sole piirpose this object I now relate, 

 from which it will be seen, I think, that theory is in this case our safer guide. 



The ground taken up by these results has been already just broken in upon, 

 as will perhaps be remembered, in a communication to this Society, entitled 

 " The Alkalinity of Carbonate of Lime,"* and while the criticism which it 

 evoked has been already useful in stimulating me to this inquiry, it will be 

 useful again, but in a different manner, by supplying us with a knowledge of 

 the precise conditions deemed necessary, by a well-known chemist, to insure 

 reliable indications when testing substances generally in respect to their 

 behaviour with the test I am employing — litmus paper. Using the precau- 

 tions recommended in this criticism, I prepared the test (litmus paper) for use 

 by simply washing it in water free from ammonia till it acquired a pale violet 

 colour, in which condition "it is a delicate test for either acids or alkalies." 



Thus prepared, the test when pressed upon them in a moist state indicated 

 the conditions of the following substances to be as stated below : — 



Alkaline. 



Carbonate of magnesia (magnesite) 



„ lime (calcareous spar) 



„ strontia 



„ baryta 



,, lead 



,, silver 

 Borate of magnesia (datholite) 



crystallized 

 Tribasic phosphate of lime cryst. 



(Ca 0)2 + HO -h PO 

 Tribasic phosphate of magnesia 



(Mg 0)2 PO 

 Apatite (Ca 0)3 + PO 

 Phosphate of silver ( A9 0)3 -h PO 

 Silicate of magnesia (olivine) 



„ „ (serpentine) 



Mica 

 Pelspar 



Acidic 



Phosphate of alumina 



(wavellite) 

 Phosphate of zinc cryst. 



(Zn 0)3 + PO 

 Phosphate of iron, 



(proto- and sesqui-) 

 Arsenite of zinc 



Neutral. 



Quartz 

 Clay 



(purest- washed) 

 Clay slate 



* See Art. LV. 



