CHEMISTRY AND THE MICROSCOPE 



description clearer. Suppose we take some common 

 table salt and dissolve it in a little water in a 

 glass, then add to this a little solution of nitrate 

 of silver, which is sold under the name of lunar 

 caustic, we shall find that a white cloudiness is 

 formed when the liquids mix, although originally 

 they were both clear. The reason of this cloudiness 

 is that the two substances, dissolved in water have 

 united with one another to form a third substance 

 which will not dissolve, therefore it settles down as 

 a fine powder. Long experience has taught ana- 

 lytical chemsts exactly what chemicals to add to 

 test for all the common substances, by the forma- 

 tion of these precipitates; so that, if any powder 

 were given to one of these scientists he could tell 

 its composition by applying certain tests. In this 

 chemical analysis considerable quantities are re- 

 quired and it is often necessary to test very small 

 samples, so small that the ordinary methods are 

 I out of the question. This is where the microscope 

 I scores, because with this wonderful instrument, 

 i only drops are required and tests of corresponding 

 ( delicacy may be made; in fact, by modern micro- 

 I scopic methods it is possible to detect the presence 

 of as little as ten thousandth part of a grain of 

 arsenic, or quicksilver or of the deadly poisons, 

 Strychnine or Prussic Acid. 



In testing for poisons the microscope is invaluable. 

 Frequently only the most minute traces of the 

 poison occur in the system and the modern micro- 

 scopist who makes a study of poisons and their 



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