474 



Prof. Guthrie on Drops, 



[Eecess, 



size of the drop is affected by the diminution in its weight caused by the 

 density of the medium. 



If W^= weight of drop of mercury in air, 



required weight of drop of mercury in liquid, 

 A = specific gravity of hquid, 

 B= specific gravity of mercury ; 



then W,= W,-4Wx. 



The values of form column 6. 



The liquid media are arranged according to the order of magnitude of the 

 numbers of column 4. The salient points of Table XV. are chiefly these : — 



1 . The drop-size of a liquid which drops under like conditions through 

 various media does not depend wholly upon the density of the medium and 

 consequent variation in the weighty in the medium^ of the dropping liquid. 

 Thus glycerine, whose density is above that of all the other liquids ex- 

 amined, does not, as a medium, cause the mercurial drop to assume either 

 its minimum or maximum size. 



2. The liquids in Table XV. are in the same order as in Table VII. 

 In other words, if there be two liquids^ A and B, which drop under like 

 conditions through air, and the drop-size of the one, A, be greater than 

 that of the other, B ; then if a third liquid, C, be made to drop through A 

 and through B, the drop-size of C through A is greater than the drop-size 

 of (u through B. 



3. Further, on comparing Tables XIII. and XV. it appears that, whether 

 water or mercury drops through turpentol and benzol, the drop through 

 benzol is greater than the drop through turpentol. This we shall after- 

 wards find confirmed in other instances into the law. If the drop-size of 

 A through B be greater thoM the drop-size of A through C, then the drop- 

 size ofD through B is also greater than the drop-size ofD through C. 



It is further observed that, while mercury exhibits its largest drop when 

 falling through air, water assumes its smallest drop-size under this condition. 



This method of the examination of liquids by drop-size in the case SLL, 

 which brings so prominently forward a comparatively slight difference be- 

 tween similar liquids, may be used, not only to detect commercial adulte- 

 rations of one liquid by another, but perhaps to distinguish between those 

 remarkably-related isomeric liquid bodies (the number of which is quickly 

 increasing) between whose terms the difference has until lately escaped 

 detection. Of these bodies perhaps the first most remarkable instance was 

 furnished by the two amylic alcohols ; but the greatest number at present 

 known is amongst the hydrocarbons. 



We may take an example illustrating the use of the stalagmometer in 

 approximately measuring the proportion, in a mixture, of its two chemically 

 aud physically similar, but not isomeric constituents. 



^^^ppose we had a liquid which we knew to consist wholly of a mixture 

 of benzol ^nd turpentol, and we wished to find the proportion in which 



