192 THE AMERICAN MONTHLY [July 
The Preparation of Crystals as Microscopic Objects. 
S. E. DOWDY. 
Few microscopic objects are more beautiful and instruc- 
tive than the crystals of various chemicals, prepared in 
such a way. as to be suitable for viewing under the micro- 
scope. Most chemists possess a microscope, often a relic 
of student days, in which owing to a dearth of fresh 
slides, they take no further interest. The obvious rem- 
edy for this state of affairs is either to purchase more ob- 
jects or to prepare some on one’s own account. Where 
possible, the latter is much the better course to adopt, as 
good home-made slides are far cheaper, more typical, and 
instructive than bought ones. These few notes will, I 
trust, serve as a rough guide to the. modus operandi to be 
observed in preparing this class of objects. The materials 
are to hand in every pharmacy, the other items required 
o ensure success, viz., knowledge of the solubilities of the 
various chemicals under trial and a certain amount of pa- 
tience, should also be to hand. The other essential re- 
puisites are a few thin 3 by 1 inch clear glass slips, some 
medium thickness round cover glasses, a small quantity 
of Canada balsam dissolved in xylol, test-tubes, spirit 
lamp, glass stirring rod, and.a small pipette. | 
Before starting work it is necessary to get the slips 
and cover-glasses perfectly clean and free from grease. 
That can be easily done by washing them with ammonia, 
rinsing with distilled water, drying them on a clean cot- 
ton rag, and finally polishing them ona piece of chamois 
leather. When these are ready, one of the three follow- 
ing methods can be adopted to prepare the slide. The 
first consists of evaporating down a saturated solution of 
the salt until enough moisture has been driven off to en- 
able the crystals to rapidly form on cooling. The prac- 
tical application of the process is as follows: Make a sat- 
urated solution of the salt in distilled water and deposit 
