160 DR. LOWIG ON THE ESSENTIAL OIL 
The undissolved portion of the oxide, which has also acquired a brown- 
ish black colour, possesses the same property. 
' The greater number of the compounds of the metals with spiroil 
may be obtained by double affinity, but for this purpose the spiroilic 
combinations must be difficultly soluble or insoluble, and very concen- 
trated solutions of easily soluble salts must be employed. For this rea- 
son, in order to obtain the combination with lime, solution of chloride 
of calcium is employed; for the combination with zine, acetate of zinc; 
for the magnesian compound, chloride of magnesium; and for the com- 
pounds with iron, the proto- and the sesqui-chloride of iron. The best 
combination of spiroil to employ is the hydrospiroilate of ammonia, 
over which the concentrated solution of the salt is to be poured. The 
spiroilide of barium, which is best obtained by saturating baryta water 
with the acid, may be advantageously employed in the state of a solu- 
tion for the preparation of several of the compounds of spiroil. The 
compounds as obtained by double decomposition are seldom crystalline, 
but are obtained almost always as a fine and soft powder. 
Spiroilice Acid. 
If hydrospiroilic acid be gently and carefully heated with nitric acid 
not too concentrated, and care be taken that the acid be not used in 
excess, the oil is converted under evolution of nitrous fumes into a so- 
lid crystalline body; the substance thus obtained is spiroilic acid. 
If the gas which is evolved during this operation be conducted into 
a solution of chloride of barium mixed with ammonia, not the slightest 
trace of carbonate of barytes will be formed. 
-. The acid is nearly devoid of odour: its taste is at first not strik- 
ing ; afterwards however much irritation in the throat, and a strong in- 
élination to cough are experienced. Spiroilic acid is fusible, and shows 
strong inclination to crystallize, especially on returning to the solid state 
after having been heated. In close vessels it may be sublimed; never- 
theless by this operation the greater part is decomposed, leaving behind 
a carbonaceous mass. 
In the anhydrous state,as it is obtained by fusion, spiroilic acid is of a 
pale yellow colour; if however it be exposed to the air it deliquesces and 
becomes of a deep yellow colour. It is easily soluble in alcohol and ether ; 
onlyslightly so however inwater. The solutions stain the skin and nails 
permanently yellow. Litmus-paper is stained deep yellow; no redden- 
ing effect can however be observed. If the alcoholic solution of the 
spiroilic acid be left to spontaneous evaporation, the acid is obtained in 
delicate transparent prisms of a golden yellow colour. 
1st,’ 0°190 fused spiroilic acid gave 0°350 carbon = 96°77 car. 
0°190 ditto gave 0:060 water=6°66 hydr. 
Qndly, 0°243 ditto gave0°450 carb = 124°42 carb. 0:0759=8'33 hyd. 
