1820.] Mr. Dalton on Sulphuric Ether. 121 



found in the usual way, provided we could guard against any loss 

 of the mixture. But such is the evaporating power of ether, 

 especially when pure, that it is impossible to pour it from one 

 vessel into another in the open air without much loss. In one 

 instance I found that after six successive dilutions and 12 trans- 

 fers, made with great care, I had lost one-fifth of the whole 

 weight used. In such case, if the diluting portions are not dimi- 

 nished duly, the results must be erroneous. ®ne circumstance 

 is favourable, the increase of density by chemical action appears 

 to be very small ; so that the densities may be calculated without 

 very material error. The following table will afford a moderately 

 good approximation, which may have its use till a better is made. 



Table of the Specijic Gravities of Mixtures of Ether and Alcohol. 

 Edier. Alcohol. Sp. Gr. 



100 + 0-720 



90 + 10 0-732 



80 + 20 0-744 



70 + 30 0-756 



60 + 40 0-768 



50 + 50 0-780 



40 + 60 0-792 



30 + 70 0-804 



20 + 80 0-816 



10 + 90 0-828 



+ 100 0-830 



From this table it would seem that ether of the second quality, 

 or that of the shops in general, contains about 25 per cent, of 

 alcohol ; and that of the third quality from 55 to 60 of alcohol ; 

 and the proportion of this article will be still greater on the pro- 

 bable supposition that pure alcohol is as low as 0-82 in specific 

 gravity. 



So far we have considered the mixtures of ether and alcohol in 

 their purest states, or nearly such ; and it has been observed that 

 in the ordinary course of manufacture, it is these mixtures, only 

 varied in proportion, that occur. But if we introduce water sa 

 as to vaiy the proportions of ether, alcohol, and water, indefi- 

 nitely, then some new phenomena occur, and the quantity of 

 ether in such mixtures is no longer to be determined by the 

 specific gravities. These mixtures are in some proportions 

 uniform throughout ; in others, they resolve into two fluids of 

 different specific gravities, alike transparent and colourless, but 

 easily distinguishable from a filmy-like surface between the two 

 fluids. Both the heavy and lioht, or as they may be called, the 

 watery and ethery fluids, contain in all cases less or more of all 

 the three ingredients. They seem to vary in their specific gra- 

 vities according to this law ; whenever the upper fluid is 

 extremely light, the under one is extremely heavy j namely, 



