SECTION III, 1916 [19] RRANS RSC: 
Factors Connecting the Concentration and the Optical Rotatory Power 
of Aqueous Solutions of Nicotine 
By ALFRED TINGLE AND ALLAN A. FERGUSON 
Presented by PRoFEssoR W. R. LANG, F.R.S.C. 
(Read May Meeting, 1916.) 
INTRODUCTION 
Our object in undertaking the investigation here described was to 
find answers to the following questions: 
1. Is the rotatory power of a dilute aqueous solution of nicotine 
4%, or less) proportional to its concentration ? 
prop 
2. Is the rotatory power of an aqueous solution of nicotine changed 
by the presence in the solution of free alkali or salts of alkali metals ? 
3. When an acid solution of nicotine sulphate is evaporated, is 
any nicotine lost by vaporisation ? Is there any loss of rotatory power 
for any other reason, such as the occurrence of racemisation. 
4. What is the rotatory power of nicotine in dilute aqueous 
solution ? 
The answers to these questions have more than an academic 
interest. Several polarimetric methods for the determination of 
nicotine have been proposed, the accuracy of which must fundamentally 
ally depend on the answers given to questions 1 and 4. We have 
devised a new polarimetric method of our own, to prove the reliability 
of which we must answer satisfactorily all the questions raised above. 
At the same time it should be noted that our determinations were 
made with an instrument designed for sugar work, and to use other 
than “D” light. The consequence is that the rotatory power of 
nicotine solutions, as determined by us, is useless for many purely 
scientific purposes. Our choice of instrument was dictated by the 
practical considerations that it is the one most often found in analytical 
laboratories, and that it is extremely sensitive. 
Previous workers seem to have assumed without experimental 
investigation that question 2 was to be answered in the negative. 
Question 3 has never been raised before, as far as we are aware. 
There is a marked difference of opinion among chemists as to 
both 1 and 4. Our own answers appear to ourselves to be quite con- 
