OF ARTS AND SCIENCES : JANUARY 28, 1863. 97 



Leopold von Rankc, of Berlin, was elected a Foreign Hon- 

 orary Member in place of the late Sir Francis Palgrave, of 

 Class III., Section 3. 



Mr. Alvan Clark read a paper entitled " The Sun a small 

 Star." 



Professor B. Peirce made a communication on the vibration 

 of solids floating in water, in reference to the displacement 

 and stability of vessels in a heavy sea. 



The following paper was presented 



On the Aluminates of Baryta, by W. P. Dexter. 



M. H. Sainte-Claire Deville has described, in the Comptes Rendus 

 for February, 1862, a "very curious compound," an aluminate of 

 baryta, soluble in about ten parts of water, and which can be made 

 to crystallize out of alcohol. The composition assigned to the crystals 

 is one atom of alumina, one of baryta, and four of water. The 

 analysis, however, leaves it uncertain whether they contain four or 

 three atoms of water. 



The existence of a compound of alumina and baryta has been long 

 known to chemists. The solubility of alumina in solution of baryta is 

 mentioned by Berzelius,* who states that alumina acts as an acid in 

 relation to the alkalies, the alkaline earths, and some of the stronger 

 metallic bases. And Vauquelinf speaks of two compounds, the one 

 soluble, containing more baryta, the other insoluble, and containing 

 excess of alumina. 



According to Unverdorben,J a neutral aluminate can be obtained 

 by dissolving alumina in caustic potash, evaporating to dryness, and 

 taking up the excess of potash with alcohol. Its solution gave, with 

 chloride of barium, a gelatinous precipitate, containing equal equiva- 

 lents of alumina and baryta, and the aluminates of other bases could 

 be precipitated in the same way. The solution of alumina in excess 

 of potash gave, with the chlorides of barium and calcium, precipitates 

 resembling the former, but containing two equivalents of baryta to one 

 of alumina ; they were dialuminates. 



The analyses of these compounds given by Unverdorben agree so 



* Traite de Chimie, Tom. II. p. 155 (Paris, 1846). 



t L. Gmelin, Bd. II. s. 296. % Pogg. Ann., Bd. VII. 



VOL. VI. 11 



