


ne — = SSS ee 
28 THE NORTHERN MICROSCOPIST. 
solution in cold water ; place a drop on centre of slide and at once 
pour off all surplus fluid, leaving as it were only a film. Put the 
slide on one side for a short time, say half-an-hour, then warm 
very gently and but slightly, and allow to cool very gradually ; 
repeat these operations until the rosette crystals are formed. This 
may occur at the first cooling, or it may take several applications ; 
sometimes in fact it is found impossible to cause them to form at 
all, and as it is noticeable that when formed, too much heat will 
cause them to disappear, it may be that too great a warmth in one 
of the warmings is the cause of their non-appearance. 
All the crystals yet described, except the last, should be mounted 
in pure Canada balsam ; but this last preparation is best mounted 
in a solution of evaporated balsam in Benzole. 
Passing now from the acids to the salts of some of the metals, I 
would direct your attention to Potassium and Sodium, which yield 
with little trouble many good forms of Micro-crystallization. These 
salts include the Arseniate, Carbonate, Chromate, and Bichromate, 
Bitartrate, Chlorate, Iodide, Nitrate, Oxalate, Ferricyanide, Ferro- 
cyanide, Sulphate, Urate, &c. Of these I need only mention one 
or two which have been brought more particularly under my own 
observation and preparation. 
As in the acids, I will refer first to one that offers but little 
difficulty to the amateur mounter—the Chlorate of Potash. The 
most typical form of this salt is that in which the crystals are each 
separate and distinct. To obtain these, it is necessary to make a 
strong solution in hot water, and to place a little of this solution 
upon a slide (previously breathing upon the slide, which causes 
the liquor to spread evenly). The slide must then be placed on 
one side, that the crystallization may proceed gradually, and if the 
solution has been made from pure chlorate, the crystals will be 
large and fine. 
For the imperfect, or as they are generally known, the dendritic 
crystals, place a little of the same solution upon a slip and heat 
over spirit lamp. Immediately the crystals begin to form at any 
point, at once tilt the slide away from that point, so that all surplus 
liquor may run off, then continue the crystallization by gentle 
warmth. 
Somewhat similar in outward appearance to the separate crystals 
of Potassium Chlorate, I may here mention those of Sodium 
Nitrate, which are, however, obtained in a slightly different manner, 
and offer a little more difficulty in the production. 
A strong, nearly saturated solution, must be prepared in cold 
water, and a drop put upon a cold slide. In a very short time 
crystals will reveal themselves as small points rising from the sur- 
face of the liquor. At once all surplus mother liquor must be 
poured away, and the slide must be gently warmed over a spirit 
