THE STUDY OF MICROORGANISMS IN THE SOIL 91 



After removing glassware from the cleaning solution rinse 

 thoroughly in distilled water. 



Dirty cover glasses and slides may be treated in the same 

 manner. Drop these, one at a time, into the dichromate mixture 

 and allow to remain for several hours. Remove from this solu- 

 tion, wash, and wipe with a soft, clean cloth. 



A simple and more rapid method, suitable for general work, 

 is to rub the shdes with moist Bon Ami, and when dry pohsh 

 them with a clean cloth. 



In order to remove fat, pass the cover slips through a flame. 

 Where it is desirable to have very clean slides and cover slips, 

 it is well to heat them in water and then in 50 per cent sulphuric 

 acid. After rinsing in distilled water, wash in alcohol and wipe 

 with a clean cloth. These should be kept in a clean, covered dish. 



A Black Finish for Table Tops 

 Method 'I 

 The following solutions are required: 



A. Copper sulphate 125 gm. 



Potassium chlorate 125 gm. 



Water 1,000 cc. 



Boil until salts are dissolved. 



B. Aniline hydrochloride 150 gm. 



Water 1,000 cc. 



Or, if more readily procurable: 



Aniline oil 120 gm. 



Hydrochloric acid 180 gm. 



Water 1,000 cc. 



By means of a brush apply two coats of solution A while hot, 

 the second coat as soon as the first is dry. Then apply two 

 coats of solution B and allow the wood to thoroughly dry. A 

 coat of raw linseed oil is next apphed. It is best to use a cloth 

 instead of a brush so as to get only a very thin coat of oil. The 

 desired amount of polish is now given the wood by rubbing in 

 the oil. In the treatment with the oil the deep black color is 

 partially brought out, although this does not uniformly appear 

 until the table has been thoroughly washed with hot soap suds. 

 This takes out the superfluous chemicals. 



The finish thus secured is an ebony black which is permanent 

 and very highly resistant to the action of chemicals, such as 

 acids and alkahes, even concentrated sulphuric acid having httle 

 or no effect if quickly washed off. 



