664 Kenneth A. MicJde : 



unoiled. Tliese were immersed in water, and the pressure 

 reduced above the water. Bubbles immediately formed on the 

 oiled minerals, and on further decreasing the pressure, bubbles 

 larger and in greater number formed on the oiled than 

 on the unoiled minerals. The nature of the bubbles on 

 the oiled and unoiled minerals were different, those on the 

 oiled being of an inverted watch glass shape when first formed. 

 On adding acid (E-gSO^) the bubbles change in character.. 

 Most of the bubbles left the unoiled quartz and gypsum, but 

 not the other minerals. At the lower pressure CO^j was evolved 

 from the calcite which was not attacked at first, showing that 

 the acid solution gets under the oil film on the mineral. With 

 a lens minute specks could be seen on the faces of the pyrite 

 crystal which gradually grew into larger bubbles on reducing 

 the pressure. On restoring atmospheric pressure the bubbles 

 became almost invisible again. The bubbles on the oiled 

 minerals were of a more permanent character and the manner 

 of leaving the minerals was also different. In the case of the 

 oiled minerals the bubbles become distorted and drag away 

 more than in the case of the unoiled minerals. On warming 

 the solution the bubbles clung much more tenaciously to the 

 sulphides than to the other minerals, the quartz, calcite, and 

 . gj^psum being almost free from bubbles. 



If a layer of oil is floated on top of water and a particle of 

 a mineral as galena or quartz is dropped on to it, the mineral 

 will only sink as far as the top of the water and remain there. 

 Minerals will sink through alternate layers of different oils 

 floating on water, and will remain floating on the top 

 of the water. If a particle of some mineral is sunk in 

 water and a layer of oil is floated on top of the water, and 

 if the pressure is reduced above the surface of the oil, the 

 mineral particle will rise as far as the surface of the water, 

 and will not penetrate the oil layer. Three beakers were taken,, 

 each containing a saturated COt^ solution in water. A layer of 

 oleic acid was added to form a layer over the surface of one, 

 kerosene in another and petrol in the third. Particles of dif- 

 ferent minerals were then dropped into the beakers, and their 

 behaviour noted. All the minerals carried down oil with them 

 in the form of a circular "blob."' CO^ gas immediately began 



