140 THE MICROSCOPE. 
in a bottle labeled “old alcohol,’ and used in the alcohol lamp for 
washing balsam off of slides, hardening animal specimens, and numer- 
ous other things that will suggest themselves. 
AxsotuTe Axconot.—It is quite expensive to buy absolute 
_alcohol for general use. I heat four ounces of sulphate of copper 
until it is thoroughly dried, and then add it to one pint of commer- 
cial alcohol and shake the mixture thoroughly and let stand for a 
few hours. The salt takes up the water and turns blue. Alcohol 
treated in this manner answers most purposes where absolute alcohol 
is wanted. The same salt can be dried and used over again for 
another quantity of alcohol. 
Lase.ine Sirpes.—Not every one stops to think how much more 
convenient it is to have the principal label on the left hand end of 
a slide. We naturally pick up a slide with our right hand and 
grasp it by the right hand end. This covers up the label on that 
end, so I make it a practice to place the label on the left hand end; 
or, if two labels are to be used, I put the main one on this end and 
the less important one on the right. 
Acacia Crment.—I find that a useful cement for finishing off 
balsam mounts is made by dissolving acacia in water and precipitat- 
ing it with alcohol and thoroughly washing the precipitate with 
aleohol until only insoluble matter remains. Make a saturated 
aqueous solution of this. To one fluid ounce of the solution add 
four drachms of the C. P. hydrated aluminum, two fluid drachms of 
glycerin, and the same quantity of water, and then strain through 
muslin. This cement drys quickly and can be followed with a 
coating of any other cement desirable. 
A Crran Crorx.—It is customary to have an old silk handker- 
chief convenient for the purpose of wiping off objectives, cover 
glasses, slides, etc. It is also quite common to see this cloth left 
out in the dust and dirt. I keep the piece of old silk in a tight box, 
so that it is not gathering dust when not in use. When it becomes 
soiled it should be washed. 
Bausam Borrites.—The mouth of a balsam bottle is usually 
smeared with balsam, so that the pipette soon becomes dirty and 
sticky. In order to avoid this I bend a piece of wire in the form of 
a quadrilateral and about the size of the greatest dimensions of the 
inside of the bottle. When this is placed in position the upper end 
serves as a support to scrape off any superfluous balsam from the 
pipette. If carefully used the lip of the bottle can be kept perfectly 
clean. 
