224 THE FIGURES OF EQUILIBRIUM OF A LIQUID MASS 



24. In all thfc experiments wliicli I have described in this memoir, I have 

 sui)i)Osed that the oil and the alcoholic mixture were rendered chemically inert 

 Aviih ro;j:ard to each other, and 1 have paid (§ G) that it was easy in a short space 

 of time to obtain two such liquids. I proceed now to detail the process by 

 means of which this object is attained. 



We begin by making a mixture of alcohol and distilled water, containing a 

 certain excess of alcohol, so that when submitted to the trial of the test tube 

 (§ 3) it h'ts the small sphere of oil fall to the bottom rather rapidly. After 

 having formed the mixture in quantity more than sufficient to till the vessel 

 which is to serve for the experiments, we introduce into this same mixture a 

 quantity of oil about double what is considered necessary for these experi- 

 ments.* If a flask is not at hand large enough to contain the Avhole, we divide 

 the masses among several separate flasks : but care must then be taken that 

 each one may contain the same proportions of water, alcohol, and oil. After 

 this we invert these flasks rapidly a great number of times, but without shaking 

 them, until the oil has been divided into spherules of the size of a pin's head ; 

 the whole is then left to rest. Then if the alcohol of the rnixture is in proper 

 quantity, the spherules should sink with extreme slowness, so as to take about 

 a quarter of an hour for the greater part to collect at the bottom of the flasks. 

 If it is otherwise, Avater or alcohol is to be added, as may be required ; the con- 

 tents to be mixed by inverting the flasks several times, as above, then left 

 again to settle, and the operation thus to be recommenced until the result is 

 obtained which I have described. When this point is obtained the whole is 

 thrown ujion filters, care being taken to cover the funm'ls containing these . 

 last with plates of glass. This precaution is necessary in order to prevent, 

 as much as possible, the evaporation of the alcohol, and for another reason, of 

 which we shall speak hereafter. The alcoholic liquor ])asses the first through 

 the filters, ordinarily carrying with it a certain number of very minute spherules 

 of oil. Wheii the greater part has thus passed, the spherules become more 

 numerous. What still remains in the first filters, namely, the oil, and a residue 

 of alcoholic liqxaor, is then thrown into a single fdtcr placed on a new flask. 

 This last filtration takes place much more slowly than the first, on account of 

 the viscosity of the oil. It is considerably accelerated by renewing the filter 

 once or twice during the operation. If the funnel has been covered with suffi- 

 cient care the oil will collect into a single mass at the bottom of the flask, under 

 a layer of alcoholic liquor. 



The preceding operations have thus given us the following results : On the 

 one hand, the inert alcoholic mixture, still holding a sm;ilL excess of alcohol, 

 and containing a certain number of small spherules of oil; on the other hand, 

 the oil equally inert, and covered with a little of this same alcoholic liquid. 

 Now, a second filtration completely clears the first from the spherules which it 

 holds. With respect to the oil, it is extracted from below the alcoholic layer 

 by means of a small siphon, armed with a lateral ttibe, and received into a dry 

 flask, which is to be perfectly corked. In this manner we have the two liquids 

 separate and inactive, with regard to each other. When it is desired to use 

 them, if we perceive that the alcoholic liquid is a little too dense, we correct it 

 with pure alcohol ; and if, on the contrary, there is too little density, we correct 

 it with alcohol at 16 degrees. In this latter case we must not use pure water* 

 • because this, when it mixes with the prepared alcoholic liquor, produces in it a 

 cloudiness more or less decided. 



The various trials I have made relatively to the above process, have led me 

 to ascertain that the two liquids, when they have not been submitted to this 

 preparation, are both modified by their mutual contact. The alcoholic liquid 



* It is indispensable to Lavo the two liquids thus in excess, on account of the quantities 

 whicii iin: ufcossaiily lost during the diffuieut operations which wo shall describe, and in the 

 preparation of the experiments. 



