Intelligence and Miscellaneous Articles. 147 



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oil employed in the barrels may be done perfectly, there will be no 

 space left but the small hole in the piston leading to its valve. 



For illustration, let us suppose the stroke to be 12 inches, and the 

 diameter of the barrels 2\ inches, or 25 tenths (as is the case in 

 Mr. Lees' pump), the diameter of the hole e one-tenth of an inch, and 

 ks length 1 inch, then, circles being to each other as the squares of 

 their diameters, we have 1 x 1 = 1 for the capacity of the hole, and 

 25 x 25 x 12 = 7500 for the capacity of the barrels ; and conse- 

 quently air, which in the receiver was 7000 times rarer than the at- 

 mosphere, would have sufficient elastic force to open the valve in the 

 piston ; but as this is a degree of rarefaction far beyond what has ever 

 been attained, or even expected, it follows that any greater nicety of 

 construction here is unnecessary. 



The above plan may, however, be objected to, on account of its 

 still leaving something to depend on the elastic force of the air which, 

 should any one consider desirable to be removed, can be done by 

 adopting metallic valves I V * with projecting points p' p', to strike 

 against the bottom of the barrels, having the spaces O' T, OT, filled 

 with oil, to exclude the external air during their shutting, instead of 

 the oiled silk ones S S' ; but even this small addition I consider 

 wholly unnecessary. — Edin. New Phil. Journ. 



GALLATES OF QUINA AND CINCHONIA. 



M. Platania forms these compounds in the following way : Pour an 

 infusion of galls into a hot solution of sulphate of quina, wash the 

 precipitate with cold water upon a filter, and dry it at 100° of Fahr. 

 Afterwards dissolve it in warm alcohol ; pour off the solution and 

 evaporate it, then add cold water to it, which precipitates pure gal- 

 late of quina. 



Another process consists in pouring gallic acid into sulphate of 

 quina, and merely washing the precipitate with cold water j and it 

 may also be formed by directly combining the acid and base each 

 separately dissolved in alcohol. Gallate of quina is very white and 

 light ; its sp. gr. is 0-816 at 60° Fahr. Its vapour is astringent, and 

 very slightly bitter j it is soluble in alcohol and aether, but almost 

 insoluble in water. It is composed of nearly 



Gallic acid 14-87 



Quina 85-13 



100-00 

 The gallate of cinchonia is obtained by dropping gallic acid into 

 a solution of cinchonia ; the gallate precipitates, and is to be re- 

 dissolved in water and suffered to cool ; the liquid becomes opale- 

 scent, and deposits granular transparent crystals. — Hensmaris Re-> 

 jiertoire de Chimie, fyc. Jan. J828. 



PREPARATION AND PROPERTIES OF ALUMINUM. 



On these subjects the following statements are made by M.Woeh- 



* The accented letters refer to a suppressed figure of the other barrel 

 of the pump. 



U2 ler. 



