Handbook of Solvents - George Wypych - ChemTech - Ventech!

15.1 Standard methods of solvent analysis 1063
isopropanol, and n-propanol. The group of panelist is asked to compare the characteristic
and residual odors of evaporation, its intensity by dilution, and its concentration. A similar
method was developed for a series of glycols. 72 Here, odor character and intensity are evaluated.
The residual odor of a drycleaning grade of perchloroethylene is determined by comparing
treated and untreated samples of bleached cotton fabric. The treated fabric is soaked
for 5 min in perchloroethylene and dried for 4 hours at room temperature. 73 Good quality
perchloroethylene should leave no odor.
15.1.23 PAINTS − STANDARDS RELATED TO SOLVENTS
The paint industry, a major user of solvents, has developed numerous standards. Some are
included in Sections 15.1.25, 15.1.31, and 15.1.35. The paint industry also uses many general
standards and some specific standards, which have not been included in any other section
of this chapter. Details of these are given below.
Sampling and testing requirements for solvents used in the paint industry are summarized
in a special standard. 74 This comprehensive list of standards used by paint industry
also includes a brief discussion of each method of testing, including sampling, specific
gravity, color, distillation range, nonvolatile matter, odor, water, acidity, alkalinity, ester
value, copper corrosion test, sulfur, permanganate time test for acetone and methanol, flash
point, purity of ketones, solvent power evaluation, water miscibility, analysis of methanol,
analysis of ethylene and propylene glycols, acid wash color of aromatic hydrocarbons, paraffins
and other nonaromatic hydrocarbons in aromatics, and aromatics in mineral spirits.
The nonvolatile matter in paints is determined by a gravimetric method after drying a
100 ml sample in oven at 105 o C. 75 The transfer efficiency of paints is a volume or weight ratio
of paint solids deposited to the volume/weight of the paint solids sprayed, expressed in
percent. This method 76 can be used to optimize the paint application process. The measurement
is done by weighing or measuring the volume of paint used on a certain sprayed surface
area and comparing this value with known or predetermined by the above method
weight of solids in the paint used for spraying.
In order to determine an ester value for solvents or thinners, the specimen is reacted
with aqueous potassium hydroxide, using isopropanol as the mutual solvent. 77 The hydrolysis
is conducted at 98 o C and the excess potassium hydroxide is determined by titration.
From the amount of potassium hydroxide consumed, the ester value is calculated.
15.1.24 pH
A method developed for halogenated solvents is applicable for determining the pH of water
extracts of solvents. 78 The solvent sample is shaken with distilled or deionized water and the
pH is determined either by comparing color upon the addition of Gramercy universal indicator
or by using a glass electrode pH meter.
15.1.25 PURITY
Several techniques are used to determine purity of solvents. Gas chromatography is the
most common and this and other methods are discussed first followed by other analytical
methods which include instrumental and simple methods. The aim of these tests is to determine
the concentration of the main component but more frequently qualitative and quantitative
determination of admixtures. Some methods have already been discussed in Sections
15.1.1, 15.1.5, 15.1.8, 15.1.9, 15.1.18, 15.1.20 and 15.1.23.
Alcohol content and purity of an acetate ester is determined by gas chromatography. 79
The method was applied to ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and 2-ethylhexyl
acetates. Water and acetic acid cannot be measured by this method and other methods are