30 



Reports were received in all from seven collaborators, and the results are tabulated 

 Citral determinations in lemon extracts and oil, 1901 . 



a Using ice water bath. 



COMMENTS OF THE ANALYSTS. 



Shook 



.1. 7'. Sy: Sample No. 2 oil globules had separated in original sample, 

 well before making determination. 



B. H. Smith: These were the first samples personally examined by this method and 

 I have not found time to repeat the work as was intended before reporting results. 



C. S. Brinton, and T. F. Pappe: We desire to state several points which will probably 

 have a bearing on the value of these results: First, the metaphenylene diamin hydro- 

 chlorid at our disposal showed signs of being somewhat decomposed and the aldehyde-free 

 alcohol, as a result, gave a quite marked coloration with the reagent. Second, although 

 we allowed several days to elapse before making up to volume our fuchsin sulphur 

 dioxid reagent, it did not become colorless but showed a deep lemon yellow tint. 



.1. F. Seeker: In laboratories where constant temperature baths are not at hand 

 and when only occasional citral determinations are required, it will be found much 

 more convenient to use ice water for immersion of reagents and colorimeter tubes. 

 Provided the standard and the unknown solutions were subjected to the same condi- 

 tions it was thought that the results might be as accurate. To test this, the constant 

 temperature bath was used in one set of determinations and in the other an ordinary 

 ether can filled with water in which a piece of ice was constantly kept. The latter 

 requires no watching and the color develops less rapidly, making it possible to read a 

 solution containing three milligrams of citral without difficulty . At 15 the color devel- 

 oped by three milligrams is a little too intense. Results at 15 are slightly higher. 



In preparation of aldehyde-free alcohol, it was found that three grams of meta- 

 phenylene diamin hydrochlorate per liter * * was sufficient provided the alcohol 

 was boiled for eight hours and allowed to stand over night. * * * 



To ascertain to what extent the aldehyde in commercial spirits used for making up 

 extracts might affect the citral determinations, a sample of ordinary 95 per cent 

 alcohol was run in the same manner as an extract. It showed aldehyde equivalent to 

 0.031 gram citral. Results obtained with extracts may thus be a little higher than 

 the truth for this reason. 



LinwoodA. Brown: In the determination of citral by the fuchsin method, the greatest 

 objection to it is in obtaining alcohol perfectly free from aldehydes. The Dunlap 

 method failed to give a perfectly aldehyde-free alcohol even after three times on the 

 same samples of alcohol, i. e., the alcohol was subjected to the method three successive 

 times. % 



The metaphenylene diamin hydrochlorid method gives the best results for this 

 determination. 



W. A. Syme: Commenting on the method for lemon extracts, I would say that the 

 method for purifying the alcohol (with metaphenylene diamin) did not yield an 

 alcohol that would not produce a color with fuchsin solution on two trials. This 

 lessens the accuracy of the work. I would suggest that other methods of preparing 

 alcohol be studied and that other solvents be tried. 



A glance at the table is sufficient to show that the results obtained in 1907 were prac- 

 tically of no value. The discordant figures on sample No. 2 are in part explained by 

 the fact that this extract was made up in 85 per cent alcohol and it was found later 

 that globules of oil had separated and were floating on the surface. This fact is noted 

 in the comments of Mr. Sy, who analyzed the sample some time after it had been 

 made up. 



The only other explanation offered, is that the analysts were not familiar with the 

 method. So far as is known Mr. Seeker is the only collaborator who had had any such 



