MICRO-CRYSTALLIZATION. 31 

ferred to, and as well as being one of the most beautiful, it is, 
of the Platino-cyanides, the most easy to prepare. Most of 
them, it will be found upon experiment, offer almost insuperable 
obstacles to any but a scientific chemist. 
To obtain these micro-crystallizations, make a strong, but not 
quite saturated solution in pure alcohol, and place a drop on cold 
slide, which should be covered with a shade of some kind to pre- 
vent the too rapid evaporation of the alcohol. A watch glass will 
answer this purpose, which allows time for the gradual building up 
of the desired crystal, but if, as frequently happens, it is found that 
good crystals have not been produced, drop upon the same spot a 
little more of the solution, this will re-dissolve the crystals already 
formed. Again cover with a shade, and in due time new and 
probably better crystals will be formed. When the crystallization 
is satisfactory and is also thoroughly dry, the slide may be mounted 
in balsam and benzole. 
Asparagine, another choice crystallization, must not be omitted. 
The finest results are obtained by making a hot saturated solution 
in water, of which solution a drop must be evaporated on the 
centre of the slide, by means of very gentle heat. - The slide must 
be removed from the influence of heat, as soon as an amphorous 
film replaces the solution, and as the slide cools the crystals will 
appear. Another form approaching closely that of wheel or circular 
crystals, described earlier in my paper, may be obtained by having 
the solution of less strength. 
It has probably been noticed that the crystals hitherto described 
have all been obtained from aqueous or alcoholic solutions, and it 
is a fact that in each case, although I have experimented with other 
solvents, as ether and chloroform, the best results have been ob- 
tained in the manner described ; but I cannot leave this part of my 
subject without mentioning two crystallizations (those of Salicine 
and Santonine) of which the best solution can be obtained by me- 
thylated chloroform ; but even in these two cases solutions do not 
give the best results, and it is noticeable that in all, or nearly all 
cases where a very volatile solvent is used, the results are not so 
good as when a slower process of crystallization can be employed. 
In the case of Salicine and Santonine a solution does not give 
so good a result as the process of fusion, and this process may be 
adopted in at least two different ways: by fusion only on the 
surface of the slip, and fusion between the slip and cover glass. 
The best results I have obtained by placing a small portion of either 
salt on the centre of slide and heating until fusion takes place ; 
and here I may warn you that a greater heat is required than in 
any other crystals mentioned, and although in other cases the slip 
may be held between the fingers, I would recommend that now a 
clip be used. One of those known as American clothes pegs 


