On Gallic Acid as a Developing Ayent in Photography. 225 



of hydrogen. Diplatinamine may in the same maimer be repre- 

 sented, with its formula written thus : — 



h 4 j ; 



in which two equivalents of ammonia have been brought into 

 play. Lastly, in furfurine we have a purely organic base, formed 

 from two equivalents of ammonia by replacement of the whole 

 of its hydrogen by three atoms of a compound radical, its formula 

 being— C 10 H 4 O 2 ] 



cioh 4 o4n 2 . 



C 10 H 4 0*J 



The view now expressed would make the constitution of the 

 bases correspond very closely with that of the acids, as explained 

 by Gerhardt. According to that chemist, a monobasic acid is 

 formed from one atom of water (viewed as H 2 0) by replacement 

 of hydrogen by a monobasic radical, while a bibasic acid is 

 formed from two atoms of water, by the replacement of two 

 atoms of hydrogen by a bibasic radical. 



I have been led into these observations by a desire to explain 

 in a more satisfactory manner than our present knowledge of 

 the bases will permit, the constitution of pyridine and its homo- 

 logues ; but I am now about to enter upon a series of experi- 

 ments, with a view of obtaining some of the bases 



X "\n X "lN X '" }N ' 



h r _ x"j 



the probable existence of which I have now indicated on theore- 

 tical grounds, which may probably form the subject of a future 

 communication. 



I may further mention, that I have found that the platinum 

 salts of pyridine and picoline undergo a peculiar decomposition 

 when boiled, platinum bases of very remarkable constitution 

 being formed. I am extending this investigation to the other 

 bases, and hope that my experiments will, at no distant date, be 

 sufficiently advanced for publication. 



XXXII. On a more convenient form of applying Gallic Acid as a 

 Developing Agent in Photography. By William Crook.es, Esq.* 



AMONG the more troublesome operations occurring in the 

 practice of photography on paper, when pursued on any 

 extensive scale, is the frequent preparation of large quantities of 

 gallic-acid solution. I believe Mr. Spillerf was the first to 

 suggest a means by which this difficulty may be practically 



* Communicated by the Author. 



t Journal of the Photographic Society, vol. ii. p. .'"<(>. 



Phil. Mag. 8. 4. Vol. 9. No. 58. March 185fi Q 



