Notes on scientific research. 115 



If one atomizes water or a solution of salt and directs the vapour against a metal 

 plate which has been carefully isolated by amber and is connected with an electroscope, 

 the latter remains at rest. On the contrary, if one atomizes a solution of a perfume, 

 the metal plate becomes positively charged when an atomizing pressure of 2 atmo- 

 spheres is employed. Whereas the vapour vanishes, on interrupting the experiment, 

 the electroscope, however, remains charged. Under the experimental conditions 

 employed by Zwaardemaker even the small drops of water which run off the metal 

 plate retain a positive charge. Zwaardemaker tested a great number of perfumes and 

 of substances having a strong odour in reference to their capacity for becoming 

 charged electrically when in a form of vapour; he obtained satisfactory results with 

 acetaldehyde, acetone, ether, ethyl alcohol, ethyl bisulphide, ethyl bromide, ethyl butyrate, 

 ethyl malonic acid, allyl sulphide, formic acid, ammonia, amyl acetate, amyl alcohol, 

 amyl butyrate, anethole, aniline, anise aldehyde, methyl anthranilate, apiol, valeric acid, 

 benzaldehyde, borneol, bromine, bromoform, carvone, quinoline, chloroform, citral, 

 citronellol, cumene, decylic aldehyde, duodecylic aldehyde, acetic acid, eucalyptole, 

 eugenol, formic aldehyde, guaiacol, heliotropine, ^sobutyl alcohol, irone, iodine, ionone, 

 linalool, menthol, mercaptane, methyl butyrate, methyl salicylate, myrtole, naphthalene, 

 nonyl aldehyde, paraldehyde, light petroleum, propylamine, pulegone, pyridine, safrole, 

 scatole, styrone, thymol, trimethylamine, undecylic aldehyde, vanilline, xylene, and 

 cinnamaldehyde. Amongst genuine perfumes no exception whatever were observed. 

 Substances like ethyl malonic acid, benzaldehyde, camphor, citral, eugenol, geraniol, 

 heliotropine, ionone, menthol, trinitrobutyltoluene are charged electrically even in 

 the most diluted solutions, others only slightly, even very little indeed, which refers 

 especially to ammonia. Chlorine water or such containing ozone, produced no 

 perceptible charge. 



If one employs a screem of metallic gauze instead of a plate, the former is charged 

 positively, whereas the particles which are driven through the screen take on a negative 

 charge; they can also be collected by means of a metal plate placed behind the screen. 

 The little drops which flow off the gauze have a much stronger odour than those 

 collected on the second screen. Strange to say, a 2 per cent, alcoholic solution also 

 produces when atomized a perceptible charge; the latter, however, becomes weaker 

 and weaker if the concentration is increased, and when a concentration of 50 per cent. 

 is used, their is no charge whatever. The same applies to acetone, pyridine, and other 

 substances. 



Surprisingly small quantities of perfumes are sufficient to produce electrical charges. 

 25-10 — 6 g. of geraniol, dissolved in 25 cc. of a 2 percent, sodium salicylate solution, 

 suffices to plainly produce an electrical charge. The same applies to the same quantity 

 of trinitro butyl toluene. Our nasal organs are, however, much more susceptible and 

 can perceive even much smaller quantities; yet it is by no means impossible that if 

 a very sensitive electroscope is employed much smaller quantities of perfumes might 

 be detected. 



Perhaps the vapour-electricity-method, might be employed for practical purposes, 

 when the question arises of proving if a perfume is at all soluble in water or not. 



Probably the molecular weight, volatility, and the reduction of the surface tension 

 are the factors which determine the quantity of a substance which is required to 

 produce the electrical charging phenomena. These are the same requirements to which 

 a compound has to conform in order to act as a perfume from a biological point of 

 view: Hence a connection between the intensity of the odour and that of the charge 

 phenomena is to be expected, a manifestation which will be most apparent in homo- 



