ON BLACK WAX. 
11 
tation of many chemical compounds by constitutional formulae for which, at 
present, there is no experimental foundation whatever; such excess cannot 
fail to be prejudicial to the advancement of real science. 
Another topic demands a few words. Chemical compounds differ in the 
tenacity with which their constituents are held together. Considerations 
connected with this have led chemists to receive the notion of two kinds of 
chemical combination, namely, combination between atoms, the ordinary 
mode, and combination between molecules as such. To the latter division 
are referred chiefly salts which contain water of crystallization. In FeS0 4 , 
7 H 2 0, for example, FeS0 4 is presumed to form one complete molecule, 
rouud which are attached the seven molecules of H 2 0 by a kind of adhesion. 
Every probability attaches to this hypothesis ; the only objection it presents 
is that of being somewhat premature. There exists a great number of com¬ 
pounds, which, with our present knowledge, can only be referred with hesi¬ 
tation to either class. The metallic hydrates furnish an example. There 
can be no doubt that caustic potash should be expressed as KHO, and also 
slaked lime Ca2HO, but whether ferric hydrate should be Fe 2 6HO or 
Fe 2 O s , 3H 2 0, it seems difficult to decide. Analogy points to the former; the 
properties of the body to the latter formula. Ferric hydrate, as is well 
known, even though never removed from contact with water, from the moment 
of its formation, and without apparent cause, changes in composition by 
parting with the elements of water. Similar phenomena are observable with 
hydrate of copper and other metals. Again, are the so-called salts of urea 
atomic, or molecular compounds ? They continually change in composition 
by mere recrystallization. Many other instances might be cited. 
Notwithstanding the advance which has been made of late years, an ad¬ 
vance which is undoubted, the number of great and difficult problems which 
yet remain to be solved is such as should remind us of the necessity that still 
remains, “ to prove all things, and hold fast (only) to that which is good.” 
ON BLACK WAX* 
BY WALTER G. SMITH, M.B. T.C.D., 
ASSISTANT-PHYSICIAN TO THE ADELAIDE HOSPITAL. 
When we meet with a number of products that are derived from the animal 
and vegetable kingdoms, and which exhibit certain characters indicating ana¬ 
logous properties, it becomes a matter of interest to investigate the nature of 
the constituents which enter into their composition. The subject of animal se¬ 
cretions is one of singular interest, especially when we compare varieties in the 
constitution of analogous secretions from different animals and under varying 
conditions of climate (Brodie). My remarks on this occasion will be confined 
to the illustration of a specimen of black wax which I subjected to analysis. 
In May, 1867, my father, while in London, purchased from Messrs. Ilearon 
and Co. a portion of a cake of black wax, of which no information could be ob¬ 
tained as to its source, except that it was imported from Madras in the year 
1862. 
The specimen, which is in the Museum of Materia Medica, Trinity College, 
Dublin, is evidently a portion of a large cake which was solidified after fusion. 
Its dimensions are 6 inches by 4, and its weight a little more than 18^ ounces; 
its thickness varies from an inch and a half to an inch and a quarter. One side 
is bevelled, and it retains the impression of the straight side of the vessel or, 
* Read at an evening meeting of the Royal Dublin Society, May 4th, 1868. 
