On the Analogies observed in Chemical Unions. 359 



Phosphoric Acid. 

 I obtained so large a precipitate, that 



I think it must form an important 



constituent of this mineral. 

 Present in considerable quantity. 

 Minute traces, but more abundant in 



another specimen from Russia. 

 Enough to give all the usual tests from 



about IJ ounce. 

 Sufficient from two ounces to give a 



precipitate with nitrate of silver. 

 Considerable traces. 

 Enough for nitrate of silver test. 

 Considerable traces from two ounces. 

 Large precipitate from two ounces. 



The quantity of phosphoric acid in 

 this substance was very considerable, 

 being equal in one instance to 2-13 

 per cent. I think most native borax 

 will be found to contain phosphate 

 of soda. 



In one specimen of this mineral from 

 Andreasberg in the Harz, the quan- 

 tity of this acid present was suffi- 

 ciently large to be estimated. I also 

 detected its presence in a specimen 

 from North America, but in neither 

 case had I enough of the mineral to 

 make another analysis. 



It is very curious that such a large quantity of phosphoric 

 acid should in these two cases be associated with boracic acid, 

 which is of a decided volcanic origin. It would be very in- 

 teresting if the substances occurring with the native boracic 

 acid in Tuscany, and also the other minerals containing boracic 

 acid, were examined for phosphoric acid. The quantitative 

 determination of the phosphoric acid in rocks would, in my 

 opinion, be of little importance, as phosphoric acid, although a 

 constant, is a very variable constituent. This, however, does 

 not apply to the simple mir.erals, such as olivine, of which it 

 forms very probably a constant constituent. 



Simple Minerals and Rocks. 

 LepidoUte, locality unknown. 



Obsidian, from Ijipari. 

 Mica, Spessart, Bavaria. 



Granite, Odenwald, Germany. 



Chlorite slate, locality unknown. 



Atigite ])orpkiiry, locality unknown. 



Mica slate, locality unknown. 



Gneiss, Odenwald, Germany. 



Two specimens of Scotch granite, lo- 

 calities unknown. 



Tincal, or native borax, from East 

 Indies. 



Datholite. 



On the Analogies observed in Chemical Unions. By ARTHUR 

 CONNELL, Esq., F.R.S.E., Professor of Chemistry, Uni- 

 versity of St Andrews. Communicated by the Author. 



In the following observations an attempt is made, by a re- 

 ference to various analogies in nature, to illustrate and support 

 some of those views regarding certain important chemical 

 unions which are more or less adopted by most chemists. 



