302 Kenneth A. Miclde : 



addition of small proportions of some substances, as saponine 

 and acetic acid. These contaminants include not only sub- 

 stances which are soluble in water, such as saponine and acetio 

 acid, but substances which are insoluble in water, such as 

 various oils and certain finely divided solid substances. 



Without doubt liquid cohesion and attachment effects are im- 

 portant factors in determining froth producing variations, 

 but it seems apparent that gas attachment is the chief factor, 

 and a comparison of the various proportions of froth produced 

 would therefore afford an approximate measurement of the 

 attachment of air to water and to various aqueous solutions and 

 mixtures. 



The following list shows the order in which a series of various 

 substances came in their froth producing effects. In each case 

 ono drop of the contaminant was mixed Avith 60 c.c. of pure 

 water and agitated vigorouslj^ with air, the froth produced being 

 noted : — • 



1. Saponine (greatest froth). 



2. Turpentine. 

 Phellandrene. 



Residual oil (from rectification of eucalyptol). 



3. Tasmanian refined petrol (0.754). 

 Acetio acid. 



4. Eucalyptol, crude shale oil (0.900). 

 Cotton se^d oil. 



5. Oleic acid. 



Combustion engine oil (0.831). 



6. Tasmanian shale residual oil. 

 Tasmanian shale turps, substitute. 

 Austral machine oil. 



7. Kerosene. 



8. Alcohol, oil of winter-green, naphtha, gasolene, ether 



(petroleum), ether (sulphuric). 

 The froth produced by the last contaminants in the series was 

 practically the same as with pure water. 



With the vieAv of obtaining some confirmation of the above 

 series of results the following experiments were carried out : — 

 1. Agitation with air, 60 c.c. of water and 10 c.c. of the 

 various contaminants. 



