478 



screens did not canse a defleciion of the galvanonietei-. Next llie 

 tube was rinsed for a quarter of an hour, or longer if need be, 

 witli dry air and tlie zero-point determined again. If tlie two zero- 

 points are approximately equal and tlie determination with the 

 odour-containing air deviates, the ratio of the diaphragm apertures 

 is that of the quantities of light transmitted, from which the absorption 

 can be calculated. 



In the same way dry air, sucked through the tliiid nnder exami- 

 nation was led through a glass v^essel |)rovided with an opening, 

 which could be closed by a glass [)late, or to which Zwaardemaker's 

 diaphragm odorimeter could be adjusted. 



By means of this ap[)aratns, a description of which will soon be 

 published, odour-containing air can be diluted to a known proportion. 

 Into a cylindrical smell-chaiuber, from which the content is inhaled 

 through a glass tube, the odorous air enters through an irisdiaphragm 

 at the bottom, while free air can enter thi-ough lateral adjustable slits. 



We estimate the dilution in which the scent almost fails to be 

 i-ecognized. So the absorptive capacity and the smell-intensity of a 

 given mixture of odorous substance and air were known. We now 

 calculated for every examined mixture how many times it had to 

 be diluted to absorb just 17o o^" '''0 incident light, and from this 

 how many olfacts such a dilution would contain. 



The subjoined table shows the results thus obtained : 



Substance 

 examined 



Number of 

 olfacts 



Substance 

 examined 



Number of 

 olfacts 



If smell-intensit\ were lelated to capacity of absorbing radiant 

 heat the above values might be expected to be approximately equal. 

 Since they are so widely different such a relation must be denied. 



1) The dilution of ether-containing air was beyond the capacity of my measuring 

 instrument. 



") In both these cases the absorption was less than ' ., perc. consequently so 

 minute as to elude measurement with my equipment. 



