NATURE 



19: 



THURSDAY, JUNE 27 



1907 



RESIKS. 



Die Harze mui die I-IarzheJiiiUer mit Einschluss der 

 Milchsdjtc. By A. Tschirch. Zweite stark 

 erweiterte Auflage. Erster und zweiter Band. 

 ,Pp. xxii+1268. (Leipzig: Gebruder Borntrager, 

 1906.) Price 32 marks. 



The Distillation of Resins. By \'ictor Schwcizer. 

 Pp. viii+183. (London: Maclaren and Sons; New 

 York : Van Nostrand and Company, n.d.) Price 

 io.<. bd. 



THE chemistry of resins has been very much 

 neglected by investigators, so much so that even 

 now the empirical formula of the best known of their 

 constituents — abietic acid, which was isolated from 

 ordinary rosin more than eighty )-ears ago — is still 

 a matter of dispute. It is difficult to account for this 

 neglect, since many of the naturally occurring resins 

 are readily resolved into crystalline or otherwise well- 

 defined substances, so that the subject does not pre- 

 sent the initial diiTiculties encountered by the investi- 

 gators who have studied the terpenes, proteids, and 

 similar intractable natural products. Resins should 

 now be particularly attractive to chemical workers, 

 since Prof. Tschirch and his collaborators have sur- 

 veyed almost the w'hole field in a preliminary man- 

 ner, and from their results it is possible to select the 

 most promising materials for detailed investigation. 



Perhaps the most important result which has 

 accrued from this work is the possibility of classify- 

 ing the constituents of the natural resins into a com- 

 paratively small number of groups of similarly react- 

 ing — and probably similarly constituted — substances. 



I.X)oked at from this general point of view, the 

 chemical work done by Prof. Tschirch and his co- 

 adjutors can be regarded as a very satisfactory con- 

 tribution to our knowledge of resin chemistry. 



The publication of the second edition of this mono- 

 graph affords an opportunity for a review of this 

 work as a whole, since the book is largely a reprint, 

 with additions and corrections, of papers published 

 in the Archiv der Pharmazie. 



Prof. Tschirch's usual method of investigation con- 

 sists in dissolving the resin under examination in an 

 indifl'erent solvent, and extracting this successively 

 with solutions of alkali carbonates and hydroxides. 



The products so isolated, and perhaps subjected to 

 a more or less satisfactory process of purification, are 

 in general regarded as definite substances, and 

 though they are in the majority of cases amorphous 

 coloured products having no constants which may 

 be regarded safely as criteria of purity, they are 

 analysed and have names and formulje assigned to 

 them. The qualifying statement that such substances 

 may be impure is no adequate defence for such a 

 proceeding, since the names and formulae are liable 

 to be copied into the literature of the subject without 

 the disclaimer which originally accompanied them. 



Similarly, when Prof. Tschirch in the course of 

 an investigation meets with a substance resembling 

 one already known, he does not in general ascertain 

 NO. 1965, VOL. 76] 



definitely whether the two "substances are identical, 

 but, assuming that they are probably distinct, makes 

 a denominator for his supposed new substance by 

 attaching a descriptive prefix to the name of the 

 older compound; thus palabictic acid, from the resin 

 of Pinus pahistris, has the same elementary composi- 

 tion and melting point as abietic acid, with which, so 

 far as one can see, it may be identical. 



The application of the terms " resinolic acid " and 

 " rescue " is also objectionable. The first of these 

 would, under any system of nomenclature now in use 

 among chemists, imply the presence of a hydroxyl 

 in addition to a carboxyl group in each of the sub- 

 stances included in the class so designated, and 

 similarly the termination -ene is usually reserved for 

 hydrocarbons. Prof. Tschirch's " resinolic acids " 

 are simple carboxylic acids, typified bv abietic acid, 

 and his " resenes " are oxygenated substances. 



The book is not only a record of the results 

 of chemical investigations, but deals with the 

 botany and habitats of the plants from which 

 resins are obtained, and to these branches of 

 knowledge the author and his collaborators 

 have made many and important contributions. 

 Much of the information given is the result of 

 personal observations made by Prof. Tschirch during 

 travels in the East Indies and elsewhere, and 

 probably no previous investigator of plant products 

 has devoted more care to securing authentic material 

 for investigation. The botanical part of the subject 

 is dealt with in the second and smaller volume, which 

 gives a resumi of our present knowledge of 

 the mode of origin and distribution of resins in 

 plants. Reference should also be made to the 

 important section dealing with latices and the resins 

 and rubbers obtained froin them, matters which are 

 at the present moment of great economic ■ import- 

 ance. 



There are a few resinous products which have been 

 the subject of investigation, and which, in spite of 

 Prof. Tschirch's desire to make his monograph as 

 complete as possible, have escaped his notice, but 

 these are for the most part of Httle importance. 



In spite of those unfortunate tendencies to add 

 unduly to nomenclature and to be somewhat lax in 

 awarding the character of a definite substance to ill- 

 defined amorphous products, to which attention has 

 been directed, this book is a welcome addition to the 

 rather scanty literature dealing with the chemistry 

 and botany of vegetable products. 



Mr. Schweizer's book is intended primarily for the 

 " practical man," and is consequently of little in- 

 terest from the purely scientific point of view. The 

 descriptions of processes and plant for the distillation 

 of rosin and the rectification of the products obtained 

 are lucid, and their value is enhanced by the well- 

 printed illustrations of distilling and other apparatus, 

 made in several instances from the author's designs. 



The chapters dealing with the manufacture and 

 uses of resinates, the preparation of lampblack, and 

 the methods of making printing and other lampblack 

 inks are of special interest, since much of the inform- 

 ation given was not accessible previously. 



K 



