CHEMISTRY. 195 



enhances the value of a classification of the elements, which is 

 founded upon the consideration of their atomicities." 



They further remark : 



" Only one point remains in which the analogy between silicon 

 and carbon is incomplete. We have said that the most charac- 

 teristic property of carbon in organic bodies is its power of combin- 

 ing directly with itself to form a complex molecule, capable of 

 combining still further with other elements, as when 2 atoms of 

 carbon, C 2 , combine with 6 atoms of Irydrogen to form the hydride 

 of ethyl, C 2 H 6 . All the bodies, thus far discussed, belong to the 

 simplest type of carbon compounds, as CEU and its analogue 

 SiH 4 ; and in silicic ethyl 4 times C 2 H 5 occupy the place of H*; but 

 Friedel and Landenburg * have lately completed the analogy and 

 obtained the body, Si 2 (C 2 H5) 6 , belonging to the same type as 

 Si 2 Hc, and C2H 6 , showing that even in its quality of forming con- 

 densed compounds silicon resembles carbon." Amer. Jour. 

 Science, XLIX., p. 307 et seq. 



Silico-Propionic Acid. By the simultaneous action of 

 zinc-ethyl and sodium upon ethyl-silicic monochlorhydrine, 

 SiCl,(OC 2 EI 5 )3, Friedel and Landenburg have obtained a liquid 

 boiling at 158.5 C., and having the formula Si(C2H5)(OC 2 H 5 ) 3 , 

 which they term tri-basic silico-propionic ether. A concentrated 

 solution of caustic potash does not set free in this compound the 

 silicon in the form of silicic acid, SiO 2 , but gives a product having 

 the formula, SiC 2 H 5 O 2 H, which, however, cannot be obtained in 

 this way in a state of purity. By heating silico-propiouic ether, at 

 180 C., in a closed tube, with chloride of acetyl, the authors 

 obtained a mixture of acetic ether and a body having the for- 

 mula SiC 2 H.5C] 3 . By treating with water the part of this liquid 

 which boils at from 90 to 110, chlorhydric acid and a white 

 gelatinous body are formed ; this last is the hydrate of silico- 

 propionic acid. When dried at 100, the acid forms a white 

 amorphous powder, greatly resembling silicic acid, but easily dis- 

 tinguished from it by its combustibility. When heated, it burns 

 like tinder, disengaging combustible gases. The acid is insoluble 

 in water, but dissolves in hot concentrated caustic potash, and is 

 not precipitated from this solution by chlorhydric acid, but only 

 by chloride of ammonium, like silicic acid, the residue after 

 evaporation being unchanged silico-propionic acid. The new 

 substance appears, therefore, to be a weak acid, analogous to 

 silicic acid, and presents the first known case of a silicic acid con- 

 taining carbon. Its formula shows that it contains/ the group, 

 SiO 2 H, which may be termed silicoxyl, and which is the analogue 

 of carboxyl, CO 2 H. It is easy to see, alse, that it forms one term 

 of a group of homologous acids. Amer. Jour. Scie?ice, from the 

 Comptes Eendus. 



Natural Organic Compounds of Silicon. At the reading be- 

 fore the French Academy of Friedel and Landenburg's paper, 

 on silico-propionic acid, Dumas remarked how readily one 

 might mistake silica, containing a greater or less amount of the 



* " Comptes Rendus," LXVIII., 18G9, p. 920. 



