CHEMISTRY. 193 



GREEN ROTTEN WOOD. 



Mr. Sorby communicates the following to the ♦' Quarterly Jour- 

 nal of Science " for July, 1868, in relation to the color of green 

 rotten wood, and whether it has any relation to the phycocyan of 

 Cohn. *' 1 have examined it carefully, and find it is quite distinct 

 from that or any other coloring matter with which I am acquaint- 

 ed. The chief constituent is a green-blue color, insoluble in 

 M'ater, and only sparingly soluble in alcohol or benzole, and not 

 fluorescent; whereas, phycocyan is soluble in water, and very 

 fluorescent. The spectra are also quite different. It gives merely 

 1 absorption band very near the extreme red ; whilst phycoc^-an 

 gives 2, both much farther from the red end. In its general 

 characters it is related to chlorophyll, but is quite distinct from it. 

 The wood also contains 2 yellow colors, which make it more 

 green ; and also a substance of a claret color, which seems to make 

 it somewhat dull. This claret color is insoluble in water, but 

 much more soluble in alcohol than the green-blue, and is quite 

 difi'erent from any other substance which has come imder my no- 

 tice. On the whole, both these colors are very interesting, since 

 they belong to classes of coloring matters which are so rare that 

 I only know one or two other examples out of some hundreds 

 which I have examined and classified." 



HARDNESS OF ANCIENT MORTARS. 



Mr. Spiller communicated a paper on this subject to the British 

 Association, in 1868, of which the following are the conclusions, 

 from the chemical examination of the ancient mortars from Burgh, 

 Pevensey, and other Roman castra : that the lime and carbonic acid 

 are invariably united in monatomic proportions, as in the original 

 limestone rock ; and that there is no evidence of the hydrate of 

 lime having at any time exerted a power of corroding the surfaces 

 of sand, flint, pebbles, or even of burned clay, with which it must 

 have been in contact for long periods. Further, that the water 

 originally combined with the lime has been entirely eliminated 

 during this process of recarbonation ; and, this stage passed, the 

 amorphous carbonate of lime seems to have been gradually trans- 

 formed by the joint agency of water and carbonic acid into more 

 or less perfectly crystallized deposits or concretions, by virtue of 

 which its binding properties must have been very considerably 

 augmented. Messrs. Abel and Bloxam assign, as one of the 

 causes of the hardening of mortars, the formation and subsequent 

 ciystallization of the carbonate of lime. 



REDUCTION OF CARBONIC ACID TO OXALIC ACID. ^ Sf ^ 



A mixture of pure sodium and dry sand was heated in a flask 

 to the boiling-point of mercury, and a rapid stream of dry car- 



17 



