CHEMISTRY AND THE MICROSCOPE 



potassium; in fact we may try any chemical sub- 

 stances we have at hand, though we shall find that 

 some do not melt very easily, and potassium chlorate 

 is somewhat dangerous, for it forms explosive com- 

 pounds with certain substances. 



The number of interesting and beautiful objects 

 which may be obtained by so-called solution tests is 

 practically unlimited, and the enthusiastic micro- 

 scopist will certainly try all the tests we describe 

 as well as many others of his own invention. Should 

 the chemist wish to detect the presence of aluminium 

 in very small quantities, he relies on his microscope 

 and proceeds in the following manner. He takes a 

 drop of the solution, suspected of containing alum, 

 and adds to it a drop of sulphuric acid. This 

 mixture he puts on his slide, which he heats over 

 a flame till dry. Now he adds a drop of water, and 

 then a very small amount of calcium chloride is 

 brought to the edge of the water. Beneath his 

 microscope he can now watch the formation of 

 beautiful colourless, eight-sided crystals which 

 denote the presence of aluminium. 



A word of warning is necessary concerning this 

 and the following experiments; they may not 

 always succeed, for success largely depends upon 

 having the solutions at the right strength, and 

 experience alone can teach us what is correct. 

 Interesting and easily formed crystals may be 

 obtained from barium sulphate, and the experiment 

 may also be made to show the phenomenon which 

 we have already mentioned, that the form of the 



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