Proceedings of the Polytechnic Association. 825 



the same treatment, was found to have a density of only 1.972. In 

 composition the two lavas do not differ materially. 



LiQtnD Glue. 



M. Knaffl states that this useful article, employed for mending 

 porcelain, glass, mother of pearl, tfec, is not nearly so good when 

 prepared with vinegar and nitric acid as that obtained by the following 

 process : Three parts of glue, broken in small pieces, shonld be covered 

 with eight parts of water, and left to stand for some liours ; one-half 

 of hydrochloric acid, and three-fourths of sulphide of zinc must then 

 be added, and the whole exposed to a temperature of from eighty-one 

 to eighty -nine degrees C, that is, from ninety-one to 128 degrees 

 Fahrenheit, during ten or twelve lionrs. The compound thus obtained 

 does not gelatinize ; and after it has been allowed to settle will be 

 found ready for use. 



Kefining Sugar. 



M. Monnier, of France, has devised a new process for refining 

 sugar. He passes into a chamber containing crude sugar a current 

 of anhydrous sulphuric acid ; a bleaching action immediately ensues, 

 three-fourtlis of the coloring matter is destroyed, while the sugar itself 

 remains unchanged. The next operation is to impregnate the sugar 

 with sulphurous acid by burning sulphur in an adjoining chamber. 

 About four parts of sulphur are used for 1,000 parts of sugar. After 

 this treatment the sugar is dissolved in water, and the sulphurous 

 acid is neutralized by lime previously converted into sucrate of lime. 

 It might be supposed that the sulphur acids would convert a portion 

 of the cane sugar into grape sugar ; but M. Monnier finds the pro- 

 portion of uncrystallizable sugar is not increased by the operation, 

 which lasts about forty-eight hours. This process gives the best 

 results with strongly colored West India sugars. 



The Coloring Matter of Perslin Berries. 



M. Schiitzenberger, at a seance of the French Academy, gave . an 

 account of his experiments with the coloring principles in Persian 

 berries, which seem to settle a point in dis])ute between Gellaty and 

 Lefort. These principles are soluble in water, but, on being boiled 

 with sulphuric acid, they are transformed into yellow pigments, which 

 are nearly insoluble. Gellaty affirmed that this transformation was 

 in consequence of the decomposition of a glucoside. Subsequently, 



