CHEMISTRY. 



179 



colorless and crystalline base, leucanilin : this 

 forms salts which are triacid. 



The formulas of the three bases now named 

 exhibit a remarkable connection a sort of 

 homology in which Ha is the constant differ- 

 ence. They are now given by Dr. Hofmann as 

 follows : 



Chrysanilin C4oHi 7 N" s . 



Rosanilin C4oHi 9 N 3 . 



Leucanilin C 4 oH2iN s . 



The same author has examined the beautiful 

 blue coloring matter obtained from crude chin- 

 olin, by action of iodide of methyl, or of ethyl, 

 &c., and termed cyanin. The iodide of thig 

 base has the formula OBoHagNal. Another and 

 homologous base, its iodide CssHwNsI, is in 

 the commercial cyanin associated with the 

 former. (Comptes Rendus, liv. 428; Iv. 817-49.) 



More recently, Hofmann has determined the 

 facts that either anilin or toluidin, pure and 

 taken singly, does not yield coloring matters 

 with oxidizing agents. Since a mixture of 

 these two bases readily yields the character- 

 istic colors, be infiers that the coloring matters 

 contain both the phenyl and tolyl molecules. 

 For the anilin blue, he has found the formula 

 C-eHail^a ; and regarding this as rosanilin in 

 which 3 equivalents of H are replaced by 3 of 

 phenyl, he considers its rational formula to be 

 C^Hn^CiaHsJaNs, and terms it triphenyl-ro- 

 sanilin. It is prepared by heating rosanilin 

 with an excess of anilin. This base, free, is a 

 white amorphous substance: its chlorhydrate 

 has a bluish-brown color, and dissolves in al- 

 cohol with a magnificent blue. The iodides 

 of methyl, ethyl, and amyl act readily upon 

 rosanilin, forming new coloring.matters analo- 

 gous to anilin blue, and which contain three 

 equivalents of one or other of the three radi- 

 cles just named, in lieu of 3H. The author 

 promises further communications on the na- 

 ture of anilin-green, anilin-violet, and azulin. 

 {Ibid. Ivii. 25.) 



V. PHYSICO-CHEMICAL Phenomena and Prin- 

 ciples. Dialysis. M. Ern. Guinet has been in- 

 vestigating the phenomena of transport through 

 porous bodies. Having experienced difficul- 

 ties in the use of the dialyser of vegetable 

 parchment [see under CHEMISTRY, prec. vol.], 

 he substituted for it a porous septum of pipe- 

 clay, similar to the material of the porous 

 cups of certain batteries. "With this he suc- 

 ceeded in repeating most of Graham's principal 

 experiments; and he also performed some 

 which with the parchment septum appeared 

 impossible. 



Thus, into a mixed solution of gum and sugar 

 was plunged a porous /vessel containing pure 

 water : in 24 hours most of the sugar had trav- 

 ersed the porous vessel and was dissolved in 

 the water, which did not, however, contain a 

 trace of gum. In like manner bichromate of 

 potassa is speedily separated from its solution 

 with caramel. M. Guinet was at the time of 

 writing experimenting with a view to obtain a 

 soluble modification of cotton, by separating 



this substance from its solution along with am- 

 moniacal oxide [query: sulphate?] of copper 

 the latter alone passing through the septum. 

 This experiment could not be made with the 

 vegetable parchment, since the latter would be 

 acted on by the ammoniacal copper. 



The author finds that the diffusibility of dif- 

 ferent crystalloids in a given liquid, as bisulphide 

 of carbon, is by no means the same. When 

 iodine, sulphur, and naphthaline are dissolved 

 in the bisulphide, the latter permeate a porous 

 vessel into pure bisulphide much sooner than 

 the former. The explanation he gives of phe- 

 nomena generally of the sort here considered, is 

 not directly chemical, or physico-chemical, as 

 that of Mr. Graham, but simply mechanical, 

 though conditioned upon differences in charac- 

 ter of the molecules of different substances. 



He supposes the porous membrane or sep- 

 tum of any sort to act merely as a sieve, 

 through which the molecules of various bodies 

 pass with greater readiness as they are more 

 attenuated. Thus, the crystalloids, which pass 

 readily, have generally a compound atom but 

 slightly complex ; while the colloids, which 

 are detained, have a high equivalent and con- 

 siderable atomic volume a consequence of their 

 highly complex atom. And the less diffusible 

 of the crystalloids are, also, those which cor- 

 respond to the greatest atomic volume (taking 

 for this, however, the quotient of the atomic 

 weight by the density, which cannot be exact). 

 Such an instance he considers as being present- 

 ed in case of the two elements, iodine and sul- 

 phur, the former of which is the less diffusible. 



Dissociation of Bodies by Heat. M. Sainte- 

 Claire Deville has made some interesting discov- 

 eries in connection with the decomposition of 

 bodies by heat. On passing through a porous 

 earthen tube a current of hydrogen, this ele- 

 ment diffuses so rapidly that the gas which issuea 

 from the other end of the tube will be found 

 to be, not hydrogen, but air. If this porous 

 tube be surrounded by a longer and shorter 

 tube of glazed porcelain, and carbonic acid be 

 passed into one end of the latter, the two gases 

 will be found to have changed places by the 

 time they have reached the other end of the 

 two tubes. 



When the tubes were heated to 1100 1300 

 C., and a current of steam passed through the 

 inner one, while a carbonic acid current is made 

 to pass through the outer tube, the gas collect- 

 ed at the other end of the tubes consisted of 

 hydrogen and oxygen gases, mixed with car- 

 bonic acid a fact showing that the steam, or 

 a portion of it, had undergone decomposition. 



Deville is led to consider the decomposition 

 of a substance as in all respects analogous to 

 the ebullition of a liquid : water is completely 

 decomposed at a temperature sufficient to ex- 

 pand its vapor to ten-fold its volume at 0. 

 The decomposition can also take place at lower 

 temperatures, the phenomenon being in this 

 respect analogous to that of the evaporation 

 of liquids below their boiling points. Deville 



