362 KANSAS ACADEMY OF SCIENCE. 



potassium hydroxide should be "pure by alcohol," the ammonia dilute, 

 and the distilled water clean as well as chemically pure. A little 

 caution here may save trouble later. 



The mirror may now be cleaned. A little nitric acid poured upon 

 the face of the speculum may be directed to all portions of the glass 

 by tipping it carefully this way and that. This will quickly clear the 

 surface of the tarnished silver. A little more acid should be used to 

 comf)letely dispose of materials that may be dissolved by acid. Potas- 

 sium hydroxide may now be used (not that mentioned above, which 

 is reserved for silvering) and distributed as was the nitric acid. 

 Further washing may be performed with clean water, and, last of all, 

 with distilled water. This should be continued till the surface of the 

 glass when dried looks clear by light reflected at an acute angle. 

 Avoid touching the surface of the mirror if possible. If, however, 

 the surface cannot otherwise be cleaned, it may be lightly and care- 

 fully wiped with a perfectly clean, soft towel, moved in circular and 

 spiral strokes. The glass should be washed again two or three times 

 after such wiping. When perfectly clean, the mirror should be put 

 aside till ready to silver. This may be done by placing it face down 

 in clean water, being careful to keep the surface from contact with 

 hard objects. A better way is to wrap the mirror tightly with 

 paraffined paper, letting the paper project three or four inches above 

 the surface to be silvered. If this is well done, the papered basin, 

 with the mirror at the bottom, should be water-tight. Pour enough 

 distilled water to cover the surface of the glass and lay a paper or 

 towel over the paper edges to keep out the dust. The mirror can be 

 silvered face up in this condition, or face down in a large vessel, if 

 preferred. 



Pour the remaining silver-nitrate solution, after making the re- 

 serve, into a clean vessel, such as a wash-bowl. Add, drop by drop, 

 the dilute ammonia, stirring briskly all the time with a glass rod. 

 The silver solution will soon change to a light brown color, and finally 

 begin to clear up again. As soon as it shows signs of clearing, stop 

 adding the ammonia and stir a moment. Now pour in the potassium 

 hydroxide. The mixture will now have a muddy brown color. Again 

 drop in carefully and slowly the ammonia, stirring vigorously. 



When it begins to clear up again, stop dropping in ammonia and 

 stir briskly. Beware of excess of amvionia. Sometimes there are 

 floating particles that refuse to dissolve, but this does not matter if 

 the liquid is clear. Now pour in slowly the reserve silver nitrate, 

 stirring continuously. Just when the liquid changes to a light 

 brown or straw color, add a few drops more to avoid excess of am- 

 monia. If, after stirring two or three minutes, the solution does not 



