Handbook of Solvents - George Wypych - ChemTech - Ventech!

15.1 Standard methods of solvent analysis 1055
The method was developed to screen organic substances for their potential to
biodegrade. If a high degree of biodegradability is determined it provides a strong evidence
that the test substance will be biodegradable in the anaerobic digestors of a waste treatment
plant and in many natural environments. Other references 9 give methods of determining of
biological and chemical oxygen demand.
15.1.4 BOILING POINT
The boiling point of solvent, its specific heat capacity, and its enthalpy of vaporization
determine the energy required for solvent separation in a distillation column. They also
determine numerous other properties of solvents (see Chapter 2).
Several methods of determination can be used, but two, distillation and gas chromatography
are the most popular. Industrial aromatic hydrocarbons are determined by distillation.
The temperature is recorded for the initial boiling point, for the sample which has been
distilled at 5%, 10%, then at 10% increments up to 90%, then finally at 95%. The temperature
should be recorded with precision of 0.1 o C. 10 A general test method to determine the
distillation range of volatile liquids 11 outlines a similar method of measurement. In addition
to the measurements at the intervals given above, the temperature of the dry point (distillation
temperature of residual quantities) is also recorded. Results must be reported as specified
in the method.
A vacuum distillation procedure is used to determine the amount of solvents in solvent-based
paints. 12 The paint sample is diluted with tricresyl phosphate, distilled for a
while under normal pressure to evaporate the more volatile solvents, followed by vacuum
distillation at 2 mm Hg.
Capillary gas chromatography is used to determine the boiling point of hydrocarbon
solvents. 13 The initial boiling point is defined as the point at which the cumulative area of
chromatogram equals 0.5% of its final total surface area. The final boiling point is at cumulative
area of 95% of the total surface area of chromatogram. The method reports boiling
point distribution in 1% intervals over the 1-99% range of the total cumulative surface area
of chromatogram as well as the initial and final boiling points. A flame ionization detector is
used in the determination and a standard solvent containing 16 known components is used
for calibration.
15.1.5 BROMINE INDEX
Two methods are used to determine bromine index of aromatic hydrocarbons which contain
trace amounts of olefins and are substantially free of materials lighter than isobutane and
have distillation end-point lower than 288 o C. The methods measure trace amounts of
unsaturations in materials which have a bromine index below 500.
The bromine index can be measured by electrometric 14 and coulometric 15 titration. In
the electrometric titration method, a sample is titrated with bromide-bromate solution (0.1
N solution of mixture of potassium bromide and potassium bromate) until the end-point increase
in potential remains steady for 30 s. 14 In coulometric titration, a potassium bromide
solution is used to titrate the solvent until the bromine concentration increases because it is
no longer being consumed by the unsaturation of the solvent. 15
Both methods can be used for setting specification, quality control, and testing of development
solvents to find olefinic content. The methods do not differentiate between the
types of unsaturations.
15.1.6 CALORIFIC VALUE
The heat of combustion of liquid hydrocarbon fuels can be determined with bomb
calorimeter. 16 Two definitions are used in result reporting: gross heat of combustion (the
quantity of energy released from fuel burned in constant volume with all products gaseous