2 THE ALUMNI JOURNAL 



Ft is a dextrogyrate: its optical rotation should not be less than 58° 

 in a 100 mm. tube at a temperature of 25°C. (77°F.). The angle of 

 rotation of the first 10% of the oil obtained by fractional distillation 

 should not differ more than 2° from that of the original oil." 



With regard to the specific gravity, I have never had any trouble. 

 On further reading the definition we come to the angle rotation which 

 as it now stands (that is 58°) I find that every oil so far tested in 

 our laboratory comes up to that standard. Previous to the 58° stan- 

 dard I had a little trouble in getting absolutely pure oil to read to 60°. 

 The next factor in the definition is that of fractional distillation ; this 

 gave me a lot of trouble, as the definition is misunderstood by a few- 

 analytical chemists. I had a consultation with a prominent oil chemist 

 about a sample of oil, and after analyzing it he reported it under 2° 

 while my report showed over 8°. On communicating with the gen- 

 tleman we discussed methods of determination, shape of flask, rate 

 of distillation, etc. 



During our correspondence he admitted using a plain distilling flask. 

 On calling his attention to tfie words "fractional distillation," he an- 

 swered, the U. S. P. meant distilling flask. I used a Glinsby frac- 

 tionating column of three beads, for one determination, and a Laden- 

 burg for another, and in both determinations obtained a distillate 

 which gave a rotation of the first 10% over 8°, and both of these oils 

 were found absolutely pure after further investigation. This is an 

 important factor in the assay of oil of lemon, as a small percentage of 

 oil of turpentine can be detected in the first 10% by the degree of 

 rotation. 



The most accurate method for the detection of oil of turpentine 



and which we could detect little as one per cent, in our laboratory, is 



as follows (which is based on the formation of Pinine-Nitriso Chlo- 

 ride) : 



Fifty c. c. of the oil are distilled with the aid of a three Glinsby 

 fractionating bulb. The first 5 c. c. of the distillate are mixed with an 

 equal part of glacial acetic acid and cooled in a freezing mixture. 

 When cold add 5 c. c. ethyl nitrite, thoroughly mix, and while still 

 in the freezing mixture add 2 c. c. of cone, hydrochloric acid, which 

 must be added very carefully drop by drop and the mixture allowed 

 to remain for a few minutes in the cooling mixture (15 minutes is 

 sufficient), when it is filtered on a Buchner funnel, using filter paper 

 under vacuum. 



