CHEMISTRY AND THE MICROSCOPE 



the saturated solution to the gelatine and. stir with 

 a glass rod, taking care to avoid the formation of 

 air bubbles. A little of the mixture may now be 

 placed in a thin film on a slide covered with a cover 

 slip and left to cool. Examination when cool under 

 the microscope will show lovely fern-like crystals, 

 whose beauty rivals that of ice crystals familiar to 

 us on our window panes during hard weather in the 

 winter. Barium chloride also produces very beauti- 

 ful fern-like crystals when treated in this manner. 

 Chlorate of potash, familiar to most of us as a 

 remedy for sore throat, forms crystals totally dis- 

 similar to those substances we have named. Having 

 made as many crystals as we wish from water and 

 also from gelatine solutions, we may turn our atten- 

 tion to gum arabic. The method of obtaining 

 crystals from this substance is exactly similar to 

 that described for gelatine except, of course, that 

 we substitute gum for gelatine. This work is of the 

 greatest interest, for not only does it yield wonder- 

 fully beautiful objects for our microscope, but it is 

 a hobby full of surprises. When we are about to 

 examine a new crystal for the first time we can 

 never so much as hazard what shape it will assume. 

 Sugar, it may be mentioned, does not crystallize 

 at once from a saturated solution in water, and the 

 best method of obtaining the crystals is to warm 

 the slide, on which we have placed a drop of solu- 

 tion, and then when dry to set aside for a day; at 

 the end of that time, especially if the air be moist, 

 the crystals will have formed. 



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