This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
265. The bath should be prepared in a large jar, being certain that all of the chemicals are completely dissolved. When ready for fixing, pour into the tank or vessel used for fixing sufficient of the solution to completely cover the films. A liberal quantity should always be used. When films are fixed the bath may be returned to the original jar and saved for the next fixing. The fixing bath may be used over and over again, so long as it fixes the films in a reasonable time, or until it becomes discolored and shows signs of staining the film, when it should be discarded and replaced with a new bath. Do not over-work the fixing bath. While films should be completely fixed in ten minutes - i. e., all the free silver removed, yet it is advisable to allow the film to remain in the bath for twenty minutes; the extra ten minutes will do no harm and will insure thorough fixing.