SCIENTIFIC NEWS! ^| 



tome time by Mr. Mollerat. It answers extremely well for 

 aromatic vinegar ; but possesses a little acrimony, on account 

 of which it is not quite so fit for the table. The wood dis- 

 tilled for this purpose yields as much charcoal as in the or- 

 dinary way, and a great deal of tar. 



In consequence of the interruption between France and Grape sugar. 

 the West Indies Mr. Proust and Mr. Parmentier have taken 

 great pains to improve the extraction of sugar from grapes*. , 



Mr. Morveau has given a history of attempts to con- Pyrometer. 

 struct instruments to measure high degrees of heat, in which 

 he does Wedgwood more justice, than he has generally re- 

 ceived in Fiance. He afterward describes an instrument of 

 his own invention sufficiently delicate to indicate changes in 

 a metallic bar that do not exceed a thirteenth thousandth 

 part of its length, Such a bar of platina is the only thing 

 sufficiently dilatable, and at the same time unalterable by 

 iire, to serve properly for a pyrometer; but the difficulty is 

 to place it on a scale, that will not dilate. This Mr. de 

 Morveau hopes soon to accomplish. 



Mr. Gay-Lussac has just explored a beautiful law of ge- Law respect . 



neral chemistry on the proportion of metal, that enters in- iog the proper* 



to each metallic salt, and that of oxieen necessary for its J?? ° ; !"^ 

 ' o J and oxigen in 



oxidation. He has shown, that a metal, which precipitates metallic saits. 

 another from an acid solution, finds in the metal precipi- 

 tated all the oxigen necessary for it to become oxided, and 

 dissolve in such a quantity, that the solution shall be neu- 

 tralized to the same degree. The quantity of oxigen re- 

 mains constant, whatever be the proportion necessary to 

 each metal : and the acid in each salt is proportionate to the 

 oxigen of the oxide, and requires so much more metal to 

 saturate it, in proportion as the metal requires less oxigen 

 for its oxidation. This law affords a very simple method of 

 determining the composition of all metallic salts; for it is 

 sufficient to know the proportion of acid in one salt of each 

 genus, to be acquaiuted with all ; and a single analysis will 

 allow us to dispense with the rest. 



Mr. Darcet jun. has shown, that soda and potash, pi*- Soda and po- 



pared with alcohol and heated to the point at which they tash cannot be 



freed from wa- 

 ter. 

 * See Journal, vol. XXI, p, 306, and 341. 



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