Acetic acid and benzene are both decomposed with violence, their cold vapors burn in fluorine, and when the latter is bubbled through the liquids themselves, flashes of flame, and often most dangerous explosions, occur.  In the case of benzene, carbon is deposited, and with both liquids fluorides of hydrogen and carbon are evolved. Aniline likewise takes fire in fluorine, and deposits a large quantity of carbon, which, however, if the fluorine is in excess, burns away completely to carbon tetrafluoride.

Such are the main outlines of these later researches of M. Moissan, and they cannot fail to impress those who read them with the prodigious nature of the forces associated with those minutest of entities, the chemical atoms, as exhibited at their maximum, in so far as our knowledge at present goes, in the case of the element fluorine.—­Nature.

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APPARATUS FOR THE ESTIMATION OF FAT IN MILK.

By E. MOLISABI.

[Illustration]

The author, after criticising the various methods for estimating fat in milk which have been proposed from time to time, agrees with Stokes (Analyst, 1885, p. 48), Eustace Hill (Analyst, 1891, p. 67), and Bondzynsky (Landwirth Jahrb. der Schweiz, 1889), that the method of Werner Schmid is the simplest, most rapid, and convenient hitherto introduced.  The conditions tending to inaccuracy are:  The employment of ether containing alcohol; boiling the mixture of milk and acid too long, when a caramel-like body is formed, soluble in ether; the difficulty of reading off the volume of ether left in the tube, owing to the gradations of the instrument being obscured by the flocculent layer of casein; when only a portion of the ether is used, fat may be left behind in the acid mixture, as shown by Allen (Chem.  Zeit., 1891, p. 331).  The author believes that by the invention of the simple apparatus represented in the accompanying figure, he has rendered the process both accurate and convenient.  This consists of a flask B of about 75 c.c. capacity, which has a glass tap fused on, with two capillary tubes attached, the one passing upward, the other downward.  The neck of flask B is ground into the neck of flask A, which holds about 90 c.c.  Either of the flasks can be placed in communication with the external air by the opening a.  The ether must be previously washed with one or two tenths of its volume of water, to remove traces of alcohol.  The operation is performed as follows:  10 c.c. of well mixed milk are weighed in (or measured into) flask A, 10 c.c. of hydrochloric acid added, and the mixture heated to boiling on an asbestos sheet.  The boiling must not exceed a minute and a half, the fluid being shaken from time to time, and not allowed to become of a deeper color than a dark brown [not black].  The flask is cooled, and 25 c.c. of ether added.