Chemical Science. 387 



Viewing these substances as mixtures, in various proportions of 

 lime and carbonate of lime, M. Vicat thought it probable they 

 might be imitated, but no mixture made by adding lime and carbo- 

 nate of lime, to each other, gave the least signs of solidification 

 under water. 



Very analogous results to these were obtained by M. Raucourt 

 de Charleville ; but the most remarkable effect was observed when 

 the fuel used was charcoal. He had prepared a mixture of pure 

 lime and clay, which, when dry was broken into small pieces, and 

 burnt, either on a heated plate or in a furnace, all the results 

 lurnished hydraulic lime, except those which had been burnt in 

 contact with charcoal. Hence, observes M. Vicat, the contact of 

 the charcoal had deranged the action which occurs between lime 

 and clay in the ordinary mode of burning, and presents a pheno- 

 menon very difficult to explain. At first, it might be supposed that 

 the iron required per-oxidation, before it would combine with the 

 lime, and that the charcoal prevented this ; but the experiments of 

 M. Berthier prove that the iron is nearly passive in these and 

 similar cases — Ann. de Chim. xxiii. 424. 



In addition to these experiments, it may be remarked, that M. 

 Clement, whilst stating the occurrence of a substance in France fit 

 for the fabrication of Roman cement, and which was discovered by 

 M. Minard, gives an opinion formed by M. Minard, from many ex- 

 periments, " that Roman cement owes its quality to a sub-carbonate 

 of lime, produced by the action of fire on the natural carbonate."— 

 Ann. de Chim. xxiv. 10o\ 



23. Nero vegetable principle, Dalhine. — M. Payen has discovered 

 a new substance in the bulbs of the Dalhia, which has been called 

 dalhine and besides it, an uncrystallizable sugar, aroma, a volatile, 

 and a fixed oil, albumen, silica, and several calcareous salts. 



To extract the dalhine, the pulp of the bulbs is to be diffused in 

 its weight of water, filtered through cloth, the liquid mixed with one 

 twentieth its weight of common chalk, boiled for half an hour, and 

 filtered. The residuum of the bulbs is then to be pressed, the solutions 

 united and evaporated to three fourths of their volume ; 4 per cent 

 of animal charcoal must then be added, and the whole clarified by 

 the white of an egg. The liquor filtered and evaporated, until a 

 film form on the surface, deposits dalhine on cooling. All the 

 washings are to be treated in the same way and thus 4 per cent of 

 dalhine, will be obtained from the bulbs. 



This substance when pure, is white, inodorous, pulverulent, taste- 

 less, of a specific gravity 1.356, more soluble in hot, than in cold 

 water, not soluble in alcohol, but precipitated by it from aqueous 

 solutions, l'otash dissolves it, ammonia does not, sulphuric acid con- 

 verts it iuto an uncrystallizable sugar more sweet than that of starch. 

 2 C2 



