The very name of this vitamine indicates its ready solubility in water. It is also soluble in 95 per cent alcohol and either of these extractants may be used to obtain the vitamine. It is not readily soluble in absolute alcohol and 95 per cent is not as good an extractant as water. Substances rich in the vitamine apparently yield the latter more readily if they have first been subjected to autolysis or if the extracting fluid is acidified. Funk was the first to show that yeast produced a greater yield if it was allowed to autolyse before extraction with alcohol. However, Osborne and Wakeman have produced a method of treating fresh yeast by boiling it with slightly acidified water which seem as efficient as autolysis in the yield produced.
The various methods of extraction now in vogue have already been discussed in Chapter II and need not be repeated here. In general it is apparent that to obtain concentrates of high potency it is permissible to employ temperatures of 100°C. if we will maintain an acid or neutral reaction but that alkali should be avoided wherever possible and when its use is imperative the temperature must be kept below 20°C. or destruction will result. In applying this rule to cooking operations the results should be determined by direct tests rather than by assumptions based on these generalizations. It should also be noted that the alkalinity of a solution should be determined on the basis of hydrogen ion concentration and not on amount of alkali added since many substances have a marked buffer reaction.
The water-soluble "B" is not only soluble in water but can be dissolved in other reagents. Thus McCollum has shown that while benzene is of little value as an extractant of this vitamine, if we will first extract the vitamine with alcohol or water and deposit this on dextrin by evaporation it is then possible by shaking the activated dextrin with benzene to cause the vitamine to pass into solution in benzene. Voegtlin and Meyers have recently shown that it is soluble in olive oil and in oleic acid and their data suggest a new means of concentrating the substance which may be of value in tracing its character.
The "B" vitamine is relatively easily absorbed by finely divided precipitates. We have already referred to the use of fuller's earth for this purpose by Seidell. This adsorptive power sometimes manifests itself in the treatment of plant extracts. A watery extract of alfalfa can be made to throw down its protein complex by diluting it to 40 per cent with alcohol. Osborne reports however that this process frequently removes the vitamine also which appears to be thrown down with the precipitated material. This adsorptive power therefore often appears as a difficulty in the handling of the substance as well as a means of extraction. We have used Osborne's method with alfalfa extracts and find the above result is not by any means invariable, for in some of our extracts we retained the greater part of the vitamine. Kaolin and ordinary charcoal are not very good adsorbents but the latter can be activated to serve this purpose.