Soap-Making Manual: A Practical Handbook on the Raw Materials, Their Manipulation, Analysis and Control in the Modern Soap Plant.Thomssen, Edgar George
Science
Soap-Making Manual: A Practical Handbook on the Raw Materials, Their Manipulation, Analysis and Control in the Modern Soap Plant.
Thomssen, Edgar George
Soap
The method adopted by the committee has been selected only after the
most careful consideration of other methods, such as the dry extraction
method and the wet method making use of the separatory funnel. At first
consideration the dry extraction process would seem to offer the best
basis for an unsaponifiable matter method, but in practice it has been
found absolutely impossible for different analysts to obtain agreeing
results when using any of the dry extraction methods proposed.
Therefore, this method had to be abandoned after numerous trials,
although several members of the committee strongly favored it in the
beginning.
IODINE NUMBER--The iodine number adopted by the committee is that
determined by the well-known Wijs method. This method was adopted after
careful comparison with the Hanus and Huebl methods. The Huebl method was
eliminated from consideration almost at the beginning of the committee's
work for the reason that the time required for complete absorption of
the iodine is unnecessarily long and, in fact, even after absorption has
gone on over night, it is apparently not complete. In the case of the
Hanus and Wijs methods complete absorption takes place in from 15
minutes to an hour, depending on conditions. Formerly, many chemists
thought the Hanus solution rather easier to prepare than the Wijs
solution, but the experience of the committee was that the Wijs solution
was no more difficult to prepare than the Hanus. Furthermore, absorption
of iodine from the Wijs solution appeared to take place with greater
promptness and certainty than from the Hanus and was complete in a
shorter time. Results by the Wijs method were also in better agreement
in the case of oils showing high iodine absorption than with the Hanus
solution and showed a slightly higher iodine absorption for the same
length of time. However, the difference was not great. The committee
investigated the question of substitution since it has been suggested
that in case of the Wijs solution substitution of iodine in the organic
molecule might occur, and found no evidence of this in the time required
for the determination, namely, 1/2 hr., or even for a somewhat longer
period. One member of the committee felt that it was not desirable to
introduce the Wijs method into these standard methods since the Hanus
method was already standardized by the Association of Official
Agricultural Chemists, but the committee felt that it must follow the
principle established at the commencement of its work, namely, that of
adopting the method which appeared to be the best from all standpoints,
taking into consideration accuracy, convenience, simplicity, time,
expense, etc., without allowing precedent to have the deciding vote.
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