358 Miscellanies. 
Sir Charles Blagden and Mr. Gilpin reduced it to 39°; Dr. Hope’s 
elegant method gave 39.5° ; Biot, in his Tables gives by calculation, 
38.156° ; and the French, in fixing their standard weights and 
measures, adopted 40°. More lately, the elaborate researches of 
Hallstrom fixed it at 39.38°, in which determination great confidence 
was placed. Prof. Stampfer, of Vienna has renewed the investiga- 
tion with the adoption of new precaution. 
His method was to weigh a hollow cylinder of known bulk, made 
air tight, at about 66° Fahr., in water of different temperatures ; and 
to insure accuracy, he continued his weighings during a whole year, 
so as to have the temperatures of the water and surrounding air nearly 
alike. From a great number of results carefully corrected, he 
deduces 38.75°, for maximum density. Muncke also has made ex- 
periments on the same subject, and found water to have a maximum 
of 38.304°. ‘The cause of differences so great must be determined 
by further investigations, the thermometers are the most likely source 
of error ; for though Erman has shown that a very minute admixture 
of a saline substance would cause an important difference in the 
temperature of maximum density, we cannot suppose such experi- 
menters to employ water that had not been several times distilled. 
Mr. Crichton of Glasgow, by employing a thermometer tube with 
a large bulb filled with water and allowing for the expansion of the 
giass, has more recently arrived at a determination agreeing very 
nearly with those of Muncke and Stampfer. The true point of 
maximum density he fixes at 38.97° Fahr. consequently that at 
which water acquires the same absolute magnitude as at 32°, 1s 
45.94°. 
5. Gallic Acid. J. G.—Dobereiner obtains pure gallic acid in a 
few minutes by the following process. A concentrated decoction of 
gall-nuts, mixed with a little acetic acid to decompose the gallate of 
lime is shaken for one minute with a quantity of ether. The gallic 
acid is taken up by the ether, and by spontaneous evaporation on a 
watch glass is obtained in small colorless prisms. If longer digested, 
the liquid separates into three portions. The lightest contains the 
gallic and acetic acids, if the latter be present in excess ; the next an 
ethereal solution of tannin ; and the heaviest, the water and extract- 
ave matter.—Report of British Association. 
6. Acetic Acid. J. G—A most important improvement has re- 
cently. been introduced into the manufacture of vinegar, which is al- 
