COAL-TAR AND WATER-GAS TAR CREOSOTES. 33 
great in number as the number of fractions taken. All readings of 
the index of refraction were, therefore, taken at the standard tem- 
perature of 60° C, a possible variation of 1° being permitted. This 
variation is corrected by the use of the factor 0.00036 per degree. 
The factor is added when the actual temperature is above 60° C, and 
subtracted when it is below. 
Sjpecijic-gravity test. — The specific gravity of the fractions was 
taken at 60° C. by means of a Westphal balance having a displace- 
ment of approximately 2 cubic centimeters. Here, again, as in the 
index of refraction, the factor for changing the readings at one tem- 
perature to those of another temperature is unknown; consequently, 
they were taken at exactly 60° C, this temperature being main- 
tained by means of a water-bath whose temperature was controlled 
to one-tenth of a degree. The density of the fractions was referred 
to the density of water at 60° C, and, as the density of water has 
been very accurately determined (13), the readings given in this 
paper may easily be transferred to those at any other temperature, 
if that is desired. The values for 60° C. given in this publication are 
higher than they would be if water at 15° C. were taken as imity, 
but may be calculated to that standard by multiplying by 0.986. 
In a few cases the volume of the fractions was too small to make 
possible the determination of the specific gravity. In such cases 
two adjacent fractions were mixed, and the gravity was recorded 
as the average of the two. This made possible a record of the gravity 
of fractions which would otherwise have been omitted. 
SulpJionation test. — The sulphonation test used was that described 
in Forest Service Circular 191. Ten cubic centimeters of the fraction 
of creosote to be tested are measured into an ordinary Babcock milk 
bottle. To this is added 40 cubic centimeters of 37/N sulphuric 
acid, 10 cubic centimeters at a time. The bottle with its contents 
is shaken for 2 minutes after each addition of 10 cubic centimeters 
of acid. After all the acid has been added, the bottle is kept at a 
constant temperature of 98° to 100° C. for one hour, during which 
time it is shaken vigorously every 10 minutes. At the end of the 
hour the bottle is removed, cooled, filled to the top of the graduation 
with ordinary concentrated sulphuric acid, and then whirled for 5 
minutes in a Babcock separator. The unsulphonated residue is then 
read off from the graduation. The readings from the major gradua- 
tions multiplied by two give the percentage of sulphonated residue 
by volume. Each major graduation is equal to one-fifth of a cubic 
centimeter, and the minor graduations are sometimes equal to 
one-twenty-fifth and sometimes to one-fiftieth of a cubic centimeter. 
In well-equipped laboratories the usual steam-jacketed ovens 
capable of maintaining a temperature of 98° to 100° C. will keep the 
reaction mixture of the sulphuric acid and creosote at the proper tem- 
75536°— 22 3 
