208 



Physical Constants. — In order to save repetition and 

 avoid ambiguity, the following explanatory note is inserted. 



Sjyecific Gravity. — The specific gravity was- taken with as 

 large a pyknometer as the amount of liquid permitted. The 

 pyknometers were standardized with water at 15° C, and 

 when the specific gravity was taken at another temperature, 

 the result was calculated to ||° C. by using a coefficient of 

 cubical expansion of 0*00075 for each '^ C. The specific gravity 

 refers to that ealculated for |-|° C, except where other tem- 

 peratures are given. 



Rotation. — Tlie rotation refers to the actual rotation in a 

 100 mm. tube. 



Refractive Index. — The refractive index was taken with 

 an Abbe refractoimeter, and the result calculated for a tem- 

 perature of 20° C. by adding or subtracting 0'00047 for each 

 °C. by which the temperature exceeds or falls short of 20° C. 

 The refractive index scale of the instrument is so arranged 

 that it reads directly the refractive index for the mean of 

 the D lines, of sodium light. 



Dispersion. — The dispersion figures given refer to the dis- 

 persion between the C and F lines of hydrogen (656"3 uu. to 

 486 1 uu.). The dispersions were taken at the same tempera- 

 ture as the refractive index, but were not calculated for 

 20° C, as the correction over a small range of temperature is 

 negligible. 



Temperature. — All thermometer readings have been cor- 

 rected for the unimraersed portion of the stem, of the 

 thermometer. 



Experimental. — The first sample of oil distilled was the 

 one used throughout in this investigation. 



A. Distillations. 



A 1. — The oil was first subjected to dry distillation. On 

 distilling the crude oil, it commenced boiling at 80° C, and 

 some acid, water, and volatile^ aldehydes distilled over first. 

 As the oil appears to suffer decomposition by prolonged heat- 

 ing at a high temperature, the quantity used for distillation 

 was 80 CCS., since this small quantity could be distilled quickly 

 and at the same time represented the minimum required for 

 tests. The following results are the average of four dis- 

 tillations : — 



Temperature. 



Amount. 



Rotation 



Below 175-5° C. ... 



7% 







175-5° C.-186° C. ... 



... 76% 



- 7° 



186° C.-207° C. 



... 10% 



-10° 



207°C.-227°C. 



3% . 



-23° 



