Eleven years have passed since the publication of the first edition. During this period enormous progress has been made, scientifically as well as practically, in the realm of the volatile oils. Numerous investigations have increased and broadened our knowledge of the volatile oils. The composition of a considerable number of volatile oils, heretofore unknown, has been revealed. New chemical compounds, the presence of which in volatile oils had, previously, not been established, have been found therein. The industry has not hesitated to utilize the results of these investigations. It has applied them to the methods of testing volatile oils and has improved these methods. The distillation of new volatile oils has greatly added to their number. All of these causes, as well as the circumstance that the first edition has been exhausted since several years, have induced me to begin work on a second edition.
Inasmuch as the material had grown too voluminous to be included within one volume, the book now appears in two volumes.
The first volume, now completed, contains the historical part, including the history of the several oils. This part had been written for the first edition by the late Dr. Friedrich Hoffmann. It remains almost unchanged and has received only occasional supplements. In addition, the first volume also contains the description of the principal constituents of the volatile oils, as well as the methods of testing them.
A new chapter has been added on the "Production of flower perfumes by extraction, enfleurage and maceration". During the past decade these methods have acquired considerable importance, more particularly in Southern France. The chapter devoted to the "Theoretical basis for obtaining volatile oils by steam distillation" has been omitted. Being of the greatest industrial importance, it was carefully revised and amplified by Dr. C. v. Rechenberg, and, inasmuch as other matters, not pertaining directly to volatile oils, had to be included in the treatise, it became so bulky as to necessitate a separate volume. This has already made its appearance under the title: "Theorie der Gewinnung und Trennung der atherischen Ole durch Destination (Grundziige der allgemeinen Destillationslehre)."
For their co-operation in the chapter: "The principal constituents of the volatile oils," which includes the principal artificial perfumes, kam indebted to Dr. O. Wiegand, Dr. A. Reclaire, Dr. H. Kohler, and Dr. W. Muller. The chapter on "The examination of volatile oils" was revised by Dr. O. Wiegand. All of these gentlemen, as well as Dr. F. Rochussen, have assisted in reading proof.
The tables contained in the first edition have been expanded and a new one has been added. Using 1,5 g. of oil and a half normal potassium hydroxide solution, this table enables the analyst to read off directly the ester value, also the percentage of ester and alcohol, without any computation. A second copy of these tables has been added to the book in such a manner that they can be used separately in the laboratory.
In the second volume, which is to appear later, the individual volatile oils are to be dealt with.
MlLTlTZ near Leipzig, July 1910.