LAWS OF THE MIXTURE OF DIFFERENT LIQUIDS. 21 



such as the solution of a salt in water, be decomposed, or a chemical attraction be 

 overcome, by its means ? 



Two liquids of different chemical properties, which are miscible together, and 

 which, therefore, have a chemical attraction for each other, mix readily at all points 

 where they come in contact.* By motion, shaking, &c., the number of points of 

 contact within a given time is increased, and the formation of a uniform mixture 

 is thus accelerated. 



If these liquids be of equal, or still better, of unequal, specific gravity, they 

 may be, with the aid of some precaution, stratified one above the other. This is, 

 in point of time, the most unfavorable case for the mixture, since proportionally 

 small surfaces come in contact. But wherever they do come in contact, it is, 

 after a very short time, impossible to detect any limit between them. 



In a cylindrical vessel containing solution of salt, the saline particles at the 

 surface are attracted and sustained by aqueous particles, which exist at the sides of 

 the saline particles and from the surface downwards. From the surface upwards, 

 the attracting aqueous particles are absent. 



Now it is evident that when the surface is brought in contact with pure water, 

 a new attraction is added to those previously existing, which acts in an opposite 

 direction, namely, the attraction of the aqueous particles floating on the surface for 

 the saline particles, and vice versa (the attraction of the saline particles to the 

 aqueous particles in contact with them.) 



At the place where pure water and brine are in contact, there is thus formed a 

 uniform mixture of the two, which upwards is in contact with pure water, down- 

 wards with brine. 



Among these three strata, of which the upper contains no salt, the lower less 

 water, a new division takes place ; the more strongly saline stratum loses salt, the 

 pure water becomes saline, and in this way salt and water are at last uniformly 

 distributed throughout the liquid. 



If we fill one limb of the tube (Fig. 7,) as far as a, with brine 

 colored blue, and the other limb with water, we find, in the course 

 of a few days, the water colored blue, and the proportion of salt in 

 both limbs equal.t It has been mentioned at p. 15, that, in a tube 

 closed with bladder, filled with diluted solution of salt, and exposed 

 to evaporation, the salt is not deposited in crystals on the outer sur- 

 face of the bladder till the whole liquid in the tube has reached, in 

 consequence of evaporation the maximum of saturation. The 

 water evaporates from the exterior of the bladder, but no salt is de- 

 posited, as long as a liquid exists within which can still dissolve 

 salt ; and in this way the heavier saline particles are distributed to- 

 wards the interior, and upwards through the whole liquid, or, what 

 amounts to the same, the lighter aqueous particles, which can still 

 dissolve salt, are distributed downwards towards the external surface 

 of the bladder. 



This distribution of salt through water takes place in the same manner as the 

 conversion of bar iron into steel.J Rods of malleable iron, as is well known, are 

 kept ignited between strata of charcoal, whereby the surface of the iron in contact 

 with the charcoal takes up carbon, and becomes a carburet of iron. The stratum 

 of iron lying next under this surface, which has the same attraction for carbon, 

 acquires carbon from the superficial stratum immediately in contact with it, and 

 in its turn gives carbon to the stratum below itself. This process, if continued 

 long enough, has no limit till all the strata of particles have acquired an equal 

 proportion of carbon, that is, till they are all saturated with it. A piece of red-hot 

 malleable iron, if kept a few moments in contact with pig iron (a carburet of iron) 

 is found to be already converted into steel at the points of contact. The mixture 

 of liquids depends on the same principle ; and we may suppose that tli^L distri- 



* Laws of mixture 9f two liquids. 



t Experiment showing the uniform mixture of two liquids. 



JThe distribution of salt through water, resembles the conversion of iron into steel by 

 cementation. 



