— I'll — 



is neutralised, phenolphthalein being employed as indicator. The 

 hydroxylamine which is not in combination with citral is then titri- 

 metrically determined with 1 / 2 normal sulphuric acid by ascertaining the 

 final reaction by means of stipple-tests with a very dilute methyl orange 

 solution. A similar course is followed in a blank test without oil of 

 lemon, in order to determine the value of the hydroxylamine solution. 

 The quantity of hydroxylamine which has entered into reaction is 

 calculated from the difference in the cc. of 1 / 2 normal sulphuric acid 

 which has been used up in each of the tests, and furtheron, the 

 amount of citral, by multiplying by 0,076. A. H. Bennett has tested 

 the value of the method with pure citral; in the case of oils of lemon 

 the citral content thus determined varied from 4,3 to 5,2 °/ . 



We were unfortunately unable to form an opinion as to the method 

 in time for the present Report, and we therefore limit ourselves here 

 to a mere recapitulation of the process. We shall return to the 

 matter in our next Report. 



A method for the colorimetric determination of benz- 

 aldehyde in extracts of bitter almonds, which resembles Mac 

 Kay Ch ace's method for the determination of citral previously dis- 

 cussed by us 1 ) has been described by A. G. Woodman and E. F. 

 Lyford 2 ). The solution of fuchsin- sulphurous acid required for this 

 purpose is prepared fresh each time in the following manner: 0,5 g. 

 fuchsin is dissolved in water, and sulphurous acid introduced into the 

 solution until the weight has increased by 20 g. when it is further 

 diluted to make 1 litre. In the next stage, alcohol free from aldehyde 

 is employed; this is obtained by taking spirit which has undergone a 

 preliminary treatment with oxide of silver, and diluting it with 25 g. 

 phenylene diamine hydrochloride per litre of alcohol, then passing a 

 strong current of air through it for three hours, and distilling off, rejecting 

 the first 100 cc. Besides this, a standard solution of freshly distilled 

 benzaldehyde in aldehyde-free alcohol (1 mg. in 1 cc.) is prepared. Next, 

 10 g. of the almond extract are diluted to 50 cc. with aldehyde-free 

 alcohol; 2 cc. of this solution is placed in a colorimeter tube and diluted 

 to 20 cc. Three control-solutions containing respectively 2, 4 and 6 mg. 

 benzaldehyde are then poured into tubes of equal size, all the tubes 

 are brought to a temperature of 15 , the contents quickly diluted with 

 20 cc. of the fuchsin-sulphurous acid solution, shaken up, and allowed 

 to stand for 10 minutes. As much of the sample-solution is now run 

 off as will make its colour resemble that of one of the control-solutions. 

 As the colour is in proportion to the degree of concentration of the 



*) Report April 1907, 116. 



2 ) Journ. Americ. chera. Soc. 30 (1908), 1607. 



