CHEMISTRY. 295 



purpose they used a therinometric reservoir containing the liquid, \vlii(;h 

 with its stem was carefully calibrated. The density found varied \c'ry 

 regularly from 230.7, where it was 0.99145, to 39'^, with a value of 

 0.87886. The expansion coefficient, was found to increase with the 

 temperature, the ratio of the increase of the volume from t to < + l de- 

 grees, to the volume at t, being at —30^, 0.001310; at — 0°, 0.001920 ; 

 at 40O, 0.002313.— (Ann. Ghim. Phys.j V, xvi, 427, 1879.) 



Friedel and Ladenburg have continued their investigations upon or- 

 ganic compounds containing silicon iu place of carbon, and have now 

 given the results of their study of the silico-ethyl series. Silicon, they 

 say, acts in a groui^ of carbon atoms like one of them, and nothing could 

 resemble a hydrocarbon more perfectly than do silicon-ethyl and silicon- 

 methyl. In their present paper they describe silicon hexaiodide Si2 le, 

 silico-oxalic hydrate H2 Sh O4, silicon hexethyl, Si2 (C2 H5)6, silicon hexa- 

 bromide Si2 Brc, and silicon hexachloride Si2 CIg. The latter has also 

 been obtained by Troost and Hautefeuille. — (Ann. Ghim. Phys., V, xix, 

 390, March, 1880.) 



De Forcraud has studied the production of new ultramarines by re- 

 placing the sodium which is contained in the ordinary blue variety, 

 more or less completely by other metals and even by organic radicals. 

 Unger had obtained a green ultramarine in which half of the sodium 

 was replaced by silver ; and Heumanu another, yellow in color, in which 

 this replacement was complete. When this latter body is heated dry with 

 a metallic or organic chloride, chloride of silver is formed and also a new 

 ultramarine. After treating of the production of the silver ultramarine 

 and the regeneration of the blue variety from it, and of the transformation 

 of the silver body into ultramarines of i^otassium and rubidium, green- 

 ish blue, of lithium, blue, of barium, yellowish brown, of zinc, violet, and 

 of magnesium, gray, the author proceeds to describe the formation and 

 properties of organic ultramarines. When the silver compound is 

 heated with ethyl iodide, a gray slightly reddish body is obtained, which 

 heated with sodium chloride gives ethyl chloride and blue ultramarine. 

 It was therefore an ethyl-ultramarine. Similar ultramarines were ob- 

 tained with the radicals allyl, amyl, and benzyl, and even with the 

 quaternary ammoniums triethyl-phenyl-ammonium and tetramethyl-am- 

 monium. — {Anii. Cliim. Phys., Y, xvii, 559, August, 1879.) 



Cooke has described a double tartrate analogous to tartar emetic, iu 

 which the potassium is replaced by silver, and which he calls therefore 

 silver emetic, or argeuto-antimonious tartrate. Although i^reviously 

 observed, its properties have been only incompletely examined since it 

 was in an amorphous condition. It is more soluble in water than at 

 first suijposed, requiring oue hundred parts of boiling Avater and less 

 than live hundred parts of water at 15° 0. for its solution. Hence by 

 dissolving in boiling water and allowing the solution to cool, colorless 

 brilliant crystals were obtained belonging to the orthorhombic system. 

 They blacken on exi)osure to light, and decompose at 200° with slight 



