D. CHEMISTRY AND METALLURGY. 103 



ble, according to Professor Dumas, that this discovery may- 

 be the initiation of a method by which the reproduction of 

 objects in nature and art may be accomplished in a degree 

 of perfection far exceeding any thing known at present, both 

 in point of rapidity and economy, not excepting photography. 

 Specimens actually exhibited to the Academy of Sciences in 

 the new art of mercuro-typy are very encouraging in their 

 promise. 3 B, December 14, 1871,599. 



DETECTION OF ALCOHOL IX WATER. 



According to M. Berthelot, the existence of alcohol in pres- 

 ence of a large quantity of water may be determined by 

 means of chloride of benzoyl. This substance is decomposed 

 very slowly by cold or lukewarm water ; but if the water 

 contain alcohol, benzoic ether is immediately formed : the 

 ether is found with the excess of the chloride of benzoyl. Its 

 presence can be made manifest by heating a drop of the chlor- 

 ide of benzoyl, which dissolves the acid chloride almost im- 

 mediately without acting at first on the ether. Even with a 

 thousandth part of alcohol the smell of benzoic ether is very 

 apparent. 21 A, November, 1871, 1093. 



DETECTION OF SULPHURIC ACID IN VINEGAR. 



The following process for detecting the 500th part of free 

 sulphuric acid in vinegar, it is stated, is sufficiently accurate 

 for all practical purposes. A fluid ounce of the vinegar to 

 be examined is, by evaporation upon a water bath, reduced 

 to about half a drachm, or the consistency of a thin extract ; 

 when quite cold half a fluid ounce of strong alcohol is to be 

 thoroughly incorporated ; the free sulphuric acid will be tak- 

 en up by the alcohol to the exclusion of any sulphates ; the 

 alcoholic liquid solution should stand for several hours and 

 then be filtered ; add to the filtrate one fluid ounce of pure 

 distilled water, and evaporate off the alcohol by the appli- 

 cation of a gentle heat ; the remaining liquid is again left 

 standing for several hours and again filtered ; to the filtrate, 

 previously acidulated with a few drops of hydrochloric acid, 

 a solution of chloride of barium is added, which, if sulphuric 

 acid be present, will yield a white precipitate. 16 A, July, 

 1872,411. 



