280 Messrs. W. H. Perkin and B. F. Duppa on the Action of 



acid. Diamond often contains cavities, and, as Brewster has 

 obserred, with accompanying circumstances which point to a 

 strong pressure in the interior, although he does not state 

 whether they contained water. 



Brewster explained his observations of the coloured rings 

 with the black cross, around the cavities, by ascribing to the dia- 

 mond a gummy consistence and vegetable origin. Simmlcr 

 suggests that it may rather be compared to that of unequally com- 

 j)re3sed glass. 



To confirm this \dew of the formation of diamonds, it would 

 be necessary to prove that liquid carbonic acid possessed a sol- 

 vent power for carbon similar to that which bisulphide of carbon 

 has for sulphui', or liquid sulphide of phosphorus for phosphoius. 

 Experiments which Simmler made in this direction with a view 

 of preparing liquid carbonic acid by Faraday's method, gave no 

 results, as the tubes always exploded. 



XLIV. On the Action of Pentachloride of Phosphorus on Malic 

 Acid. ^//William H. Perkin, F.C.S., atidB. F. Duppa, 

 Esq.* 



THE study of the action of bromine on acetic acid, Avith which 

 we have been engaged for some time, has yielded two new 

 acids, representing acetic acid in which one and two equivalents 

 of hydrogen ai'e replaced by bromine. 



These acids, bromo- and bibromo-acetic, w^hen treated with 

 hydrate of silver or potassium, decompose, yielding a bromide 

 and two other acids ; thus, — 



C4(H=^Br)0'* + AgH02=C4H'»06-|-AgBr. 



Bromacetic acid. Glycolic acid. 



C''(H2Br2)0'i + 2AgH02=C4H4 08 + 2AgBr. 



Bibroniacetic acid. Glyoxylic acid ? 



These acids, it will be observed, differ in composition from 

 acetic acid by containing two and four equivalents of oxygen 

 more than it, and, strange to say, although representing two 

 and three molecules of water, appear to be (under ordinary cir- 

 cumstances) monobasic. 



Now there are two bibasic acids known, bearing a similar rela- 

 tion in composition to succinic acid as the above do to acetic, as 

 may be seen by the following Table : — 



C W 0* Acetic acid. C^ H^ 0« Succinic acid. 



C4H4 06 Glycolic acid. C^H^Oio Malic acid. 



C^H^O^ Glyoxylic acid. C^H^O'^ Tartaric acid. 

 * Communicated by tlie Authors. 



