— 106 — 



Of these cylinders, in the above arrangement of experiments, 

 /3-ionone and isoirone have a pleasant violet odour, but only in the 

 vicinity of the limit of perception, at most up to an intensity of 

 5 olfactiae; all other cylinders have a herb-like odour. 



When diluted to I : io G all ionones have equal odour-intensity 

 (0,1 cm.) and the violet-character becomes distinctly noticeable. 



More exact measurements were taken with the above-described 

 aspiration method. As it appeared desirable in the production of the 

 perfume-solutions, to start from a physically exactly defined condition, 

 which in theory has a more definite value than any arbitrary degree 

 of dilution, a so-called heterogenous equilibrium was arranged on the 

 magazine cylinder, by leaving the latter for a prolonged time in con- 

 tact with water and camphor or some other odorous substance. There 

 is then a system of two components (water with camphor), and three 

 phases (solid, liquid, and gaseous); provided the temperature and the 

 height of the barometer do not vary too much, the composition of 

 the phases remains constant. As soon as the cylinder is shifted, and 

 the continuous current of air disappears from its internal surface, the 

 gaseous phase is removed. The evaporation of water and odorous 

 substance, however, always takes place in the same proportion. If, 

 therefore, the composition of the gaseous phase has previously been 

 determined, it is possible to deduce from it the composition of the 

 vapour which is liberated in the olfactometer. It is only necessary 

 to calculate its degree of concentration from the total rapidity of evap- 

 oration of the liquid. The concentration of the odorous substance 

 in the smelling flask is so great in this method of testing, that dilution 

 is necessary for the purpose of determining the limit of perception. 

 This is best done if necessary by repeatedly evacuating the smelling 

 flask, and letting inodorous air pass through. 



A few examples are given below: 



i. Camphor water. System of two components and three phases. 

 Approximate composition of the saturated solution of camphor i : i o 3 , at 1 2°. 

 Limit of perception at 0,7 cm./ 10 = 0,07 cm. 

 „ 3,0 cm./i6 = 0,19 * 

 „ 6,0 cm./20 = 0,3 „ 



The camphor vapours consequently have a comparatively more 

 powerful odour when in greater concentration, than when diluted. 



2. /?-ionone, i°/ 00 alcohol. Solution brought to an assumed system 

 of equilibrium by means of water (three components, and two phases). 



Limit of perception at 2 cm./ 100 = 0,02 (faint violet odour). 

 At 2 cm./ 20 = 0,1 cm. (faint herb-odour). 



The advantage of producing a heterogenous equilibrium lies in 

 this, that the passing of the odorous substance is proportionate to the 



