Chemical Science, 353 



24. Convei'sion of Gallic Acid into XJlmin by Oxygen Gas. — Ac- 

 cording to Dobereiner, when a solution of Gallic acid in liquid 

 ammonia is placed in contact with oxygen gas it gradually absorbs 

 as much of the latter as is requisite to convert the whole of its 

 hydrogen into water : 100 parts of the acid absorb 38.09 parts 

 of oxygen. In the ordinary atmospheric temperature, the ab- 

 sorption is complete at the end of from 18 to 24 hours. While 

 this change is going on, the solution becomes intensly brown 

 coloured and opaque ; and on the addition of muriatic acid, it lets 

 fall a pale-brown coloured flocculent substance, which possesses 

 all the characters of ulmin. From this experiment, Doberei- 

 ner considers it probable that ulmin consists of an atom of oxide 

 of carbon (=12 carbon + 8 oxygen*) in combination with an 

 atom of water (= 1 hydrogen + 8 oxygen) : it is certain, at 

 least, that if the details of the experiment be accurate, the con- 

 stituents of the Gallic acid, (according to Berzelius's analysis) 

 taken in conjunction with the absorbed oxygen, are resolvable 

 into this simple ratio of atoms. 



Gallic acid, prepared by Scheele's process, even after having 

 been crystallized from absolute alcohol, absorbs considerably 

 less oxygen than the sublimed acid, and it appears, therefore, 

 to be still contaminated with tannin, or with some other foreign 

 admixture. — Ann. Phil., N. S.^ ix. 390. 



25. Presence of Oxalic Acid in the mineral Kingdom, in enormous 

 quantities^ in certai?i plants, and on its advantageous preparation; by 

 M. H. Braconnot. — Whilst botanizing, some time since, M. Bra- 

 connot collected a yellowish matter from a cavity in a calcareous, 

 rock, which, examined at the time, did not effervesce with acids, 

 or contain any notable quantity of lime ; and was found, some time 

 after, by treatment with carbonate of soda, to contain a consi- 

 derable quantity of oxalic acid. Not supposing it could be a 

 vegetable production, inasmuch as the rock was steril, and 

 yet surprised at it, as a mineral body, he examined the place 

 again, and finding certain crustaceous lichens growing there, he 

 was again struck with an observation he had previously made, 

 of the enormous quantity of lime in some of these plants, amount- 

 ing to as much even as IS per cent. The analysis referred to is in 

 the Annates de Chimie.^ vi. 133 ; and there, the IS parts of lime 

 are considered as united to 34 parts of an unknown vegetable 

 matter. This was now found to be oxalic acid, and in smaller 

 quantity (29.4). 



The following experiment will readily account for the presence 

 of oxalate of lime in inorganic natural substances. Some of the 

 common varioluire was collected from the surface of an old 



* This oxide of carbon is of course merely hypothetical. 

 Vol. XIX. 2 A 



