16 



Report of Schimmel 8j Co. April/October 1917. 



logous series. J. Passy 1 ) has referred to this fact in his notes on the intensity of the 

 odour of aliphatic alcohols. He applies the term minimum perceptibile to the smallest 

 quantity contained in one litre of air which can still be smelt. If one divides the 

 value of this quantity expressed in grams by the molecular weight of the substance 

 and the result again into 1, one obtains the spec, intensity of smell. For the above- 

 mentioned alcohols and acids one finds under these conditions the following values: — 



Table I. Intensity of odour of aliphatic alcohols. 



Minimum perceptibile 



Molecular 



Specif, odour 



Log. mol. 



expr. in grs. per litre. 



weight. 



intensity. 



intensity of odour. 



Methylalkohol . . 



.1000-10-6 



32 



0.032-106 



0.51 



Ethylalkohol . . 



. 250- 10-6 



46 



0.18-106 



1.26 



Propylalkohol . . 



. 10 to 5- 10-6 



60 



6-106 



2.78 



Butylalkohol . . 



. 1-10-6 



74 



74-106 



3.87 



Zsoamylalkohol 



. 0,1-10-6 



88 



880- 106 



4.94 



Table II. Intensity of odour of fatty acids. 







Minimum perceptibile 



Molecular 



Spec, odour 



Log. mol. 





expr. in grs. per litre. 



weight. 



intensity. 



intensity of odour 



Formic acid . . 



. 25-10-6 



46 



18-10 6 



0.26 



Acetic acid . . 



. 5-10-6 



60 



120-10 6 



1.08 



Propionic acid . 



. 0.05-10-6 



' 74 



1480-106 



3.17 



Butyric acid . . 



. 0.001-10-6 



88 

 102 

 116 



88000-106 



10200-106 



2900-106 



4.94 



Valeric acid . 



. 0.01-10-6 



4.01 



Caproic acid . . . 



. 0.04-10-6 



3.46 



CEnanthylic acid 



. 0.3-10-6 



130 



430-106 



2.63 



Caprylic acid . . 



. 0.05-10-6 



144 



2880-10 6 



3.46 



If one plots out the mol. weights on to the abscissa and the mol. odour intensities 

 on to the ordinata of a coordinate system, one obtains exceedingly regular lines. 



Even the charge capacity of the vapours can be demonstrated. If one places a 

 tin disc at a distance of 1 to 2 mm. in front of the atomizer, the former remains 

 uncharged. If one removes it, however, from the atomizer, its charge grows in a 

 direct ratio to the distance, up to a certain maximum; when once this has been 

 surpassed, the charge diminishes again and finally disappears altogether at a certain 

 distance which is characteristic for every substance. Zwaardemaker calls this distance 

 the critical one. 



Table III. Critical distance for aliphatic alcohols expressed in centimeters. 

 Substance. 0.3 normal. 



Methylalkohol 46 



Ethylalkohol ..... 103 



Propylalkohol ..... 145 



Butylalkohol 170 



Jsoamylalkohol .... 187 



One obtains a graphical representation of the tables I and III if one plots out the 

 values of the molecular weights on to the axis of the abscissa and the logarithm of 

 the values of the spec, odour intensities and the critical distances on to the ordinates. 



0.2 normal. 



0.1 normal 



26 



3 



70 



35 



80 



72 



100 



117 



135 



130 



l ) Compt. rend. 114 (1892), 306, 1140; 116 (1893), 1007. 



