i 9 4 THE MICROSCOPE. 



angled one — th, and after he had unscrewed the cover, gave the 

 objective a vigorous wipe to restore its brilliancy. 



How it did shine ! Like a star of the first magnitude ; but as 

 soon as I saw it I exclaimed, " You have ruined it ! " 



" How so ? " he asked in dismay. 



"You have applied a preparation of mercury, and amalgamated 

 the brass. In a few minutes it will crack all to pieces," said I. I 

 thought it possible, however, to put the cylinder in the flame of a 

 spirit-lamp and drive off a portion of the mercury, and thus decrease 

 the brittleness of the amalgam, and proceeded to try it. But even 

 while I prepared the lamp the objective commenced to disintegrate, 

 and soon that wide-angled one — th was a heap of ruined amalgam. 



This is trick (or fake, as it is technically called in the argot 

 of the noble brotherhood of fakirs) number one to which I wish to 

 call the attention of microscopists. Those innocent little ten cent 

 bottles of " magic plating fluid " have ruined many a valuable bit of 

 brass and copper work. I remember a half-dozen instances, within 

 my own ken, where the damage could not be repaired for fifty dol- 

 lars. Let every reader of The Microscope beware of them. In my 

 opinion there is hardly any metal handsomer than well-polished and 

 lacquered brass, but if you must plate your instruments the follow- 

 ing formula will give you a really good, genuine silver plating 

 fluid : • 



Dissolve 50 grains of crystallized silver nitrate in an ounce of 

 distilled water. In a separate vessel dissolve 100 grains of potas- 

 sium cyanide in 2 ounces of distilled water. Mix the two solutions 

 slowly, stirring with a glass rod. In still another vessel dissolve 50 

 grains of common salt (sodium chloride) in 5 ounces of distilled 

 water, and when the solution is complete add to it the solution of 

 silver cyanide. This fluid should be kept in an orange-colored bot- 

 tle (though if the chemicals and water are all pure, this precaution 

 is not necessary), and well stoppered. It will silver any metal in 

 ordinary use. Iron or steel, to be silvered evenly and firmly, should 

 be dipped for a minute in a bath of nitric acid of 1.2 Beaume, and 

 rinsed in distilled water immediately before being placed in the sil- 

 vering solution. Bear in mind that, to get the best results in this, 

 as in every other process, absolute cleanliness is necessary. If you 

 wish a silvering fluid for brass or copper only, the addition of the 

 sodic chloride is not essential, and, in its stead, common precipi- 



