ON THE PREPARATION OF MICROSCOPIC CRYSTALS. 
269 
much better than others, and it will be noticed that those which have formed 
most rapidly are the best. Perhaps of all microscopic crystals these are the 
most beautiful, and certainly are not difficult to prepare. 
The second method is to prepare the pure salt by adding tincture of iodine to 
a solution of 10 grs. of bisulphate of quinine in ^ oz. of acetic acid; as long as 
the crystals are thrown down, these are to be collected and purified by one or 
two recrystallizations. 
A small portion of the pure crystals should be dissolved in spirit of wine by 
the aid of heat, the solution allowed to become nearly cold, and when the 
crystals are just on the point of separating, a drop or two should be poured 
on to a slide ; when the crystals are of sufficient size, the superfluous liquid, if 
any, should be poured off. These crystals, if preserved as permanent objects, 
are best mounted dry. 
Some of the most interesting microscopic crystals are, as is well known, de¬ 
rived from urine ; and although, for pathological purposes, it is essential they 
should be deposited without any interference, yet some methods may be here 
given for preparing them, or rather of assisting their deposition. For all the 
following experiments the urine, having been allowed to cool, should be filtered, 
to remove mucus, extraneous matters, etc. 
If hydrochloric acid is added to urine, and the fluid allowed to stand, crystals 
of uric acid will separate after a time, but they seldom possess any distinct 
form. Uric acid in characteristic crystals will be best obtained by allowing 8 
or 10 oz. of urine to stand some hours after the addition of 2 or 3 drms. of 
acetic acid. In a day or two the crystals will have grown larger ; the bottle 
should then be well shaken to detach them from the sides, and the crystals 
washed with distilled water, acidulated with acetic acid. To obtain the rarer 
forms it is requisite to allow the crystals to deposit as quickly as possible, but 
as urine contains normally so small a quantity of uric acid, this is not practic¬ 
able, unless the deficiency is artificially supplied. This may be done as follows : 
make a solution of urate of sodium by boiling uric acid (or the solid white 
urine of serpents) with solution of caustic soda, until no more is taken up. If 
1 or 2 drms. of this is put into 8 oz. of urine, and a small quantity of acetic 
acid added, not more than sufficient to neutralize the soda, very perfect crystals 
wall be obtained. These crystals, with the exception of being a little lighter co¬ 
loured, will be similar to what are found in urinary deposits. By varying the 
quantity of urate of sodium and of acetic acid, many varieties of crystals may 
be produced. If uric acid, which has been prepared from serpents’ urine, be 
boiled with lime-water, a small quantity will be taken up, and if this is put into 
urine and acetic acid added, the same results will be obtained. This process 
sometimes produces better crystals than the former. 
Very beautiful crystals of uric acid may be made by adding to the above so¬ 
lutions of urate of sodium and urate of calcium, small quantities of different 
acids largely diluted with water. In almost all cases different results will be 
obtained. If the crystals are deposited from hot solutions, they differ from 
those deposited from cold ; and if the quantity of acid employed is varied, the 
crystals vary also. 
Another deposit found in urine is the phosphate of ammonium and magne¬ 
sium or triple phosphate. It is generally met with in two forms, namely, 
prisms and so-called stellate crystals. These may both be easily prepared by 
the following methods:—for the first, a small piece of carbonate of ammonium, 
about 25 or 30 grains, should be dropped into 8 or 10 oz. of urine, and allowed 
to remain perfectly quiet for some hours ; crystals will then be observed floating 
near the top, and clinging round the sides of the bottle; if they are of suffi¬ 
cient size, the bottle may be gently shaken to send all the loose crystals to the 
bottom, and the urine poured off. It is well to gather all the loose crystals 
