334 



NATURE 



lAzig. 27, 1874 



himself heart and soul to his work : the requisite know- 

 ledge he evidently possesses, and he has shown good 

 judgment in selecting from much new matter what to bring 

 forward and what to withhold. Neither in arrangement 

 nor in substance has he made direct use of previous 

 treatises on the subject ; he has written his own book 

 on organic chemistry, and it certainly will prove to be a 

 good and useful one. 



No treatise of note on this subject had appeared of late 

 years in our language, and this rapidly developing branch 

 of science had outgrown the old form in which it had 

 been cast. The change of name which has been suggested 

 is really indicative of the change the science has under- 

 gone : formerly it was Organic Chemistry ; now it is the 

 Chemistry of the Carbon Compounds ; in fact, formerly it 

 was the properties of a few substances, the direct pro- 

 ducts from organised structures, which was studied, 

 whereas now a very large portion of a treatise on organic 

 chemistry is taken up with the exposition of the theore- 

 tical constitution of artificially prepared bodies. In few 

 branches of science has theory been more useful and 

 productive of more good than in this branch of chemistry ; 

 and certainly inorganic chemistry, although dealing with 

 simpler bodies, owes much to lessons derived from the 

 organic branch of the subject. 



Dr. Armstrong has grouped his subjects in a simple, 

 and, if in somewhat a summary, still in a philosophic 

 way. He casts off and entirely ignores all bodies which 

 at present refuse to fall into some established group. 

 Thus, such bodies as the natural organic alkaloids, indigo, 

 albumen, &c., find at present no place in his book ; while 

 we do not regret the exclusion of bodies of doubtful 

 composition, unknown constitution, and but little special 

 interest, still, to ignore the whole of the well-defined class 

 of natural alkaloids was hardly necessary as a matter of 

 principle, and certainly will prove inconvenient to the 

 student. 



Since this special property of carbon, this power which it 

 has of combining with itself, appears capable of yielding an 

 almost infinite number of compounds, the classification 

 of this host of bodies becomes a matter of the first im- 

 portance. So few were the number of organic bodies 

 known only some forty years ago, that they could be 

 classed according to their origin as vegetable or animal 

 substances ; afterwards there sprung up a multitude of 

 bodies formed directly or indirectly from these, and we 

 have the first indication of those series of bodies which are 

 now so characteristic of organic chemistry. More or less 

 of the old principle of grouping has lingered in the science 

 until now, but in this book it gives way entirely to group- 

 ing dependent solely on constitution ; some of the many 

 series of organic bodies are now tolerably complete, and 

 the discovery of new bodies, instead of as formerly tend- 

 ing to complicate the science, now tends to simplify it. 

 In this arrangement of the compounds in series. Dr. 

 Armstrong introduces a simplification which is important ; 

 he does away with the aromatic group of compounds as 

 a distinct group, and merges them in the larger general 

 groups. This aromatic group of compounds, as they have 

 been designated, have undoubtedly very marked and 

 specific properties, but Dr. Armstrong shall state for him- 

 self his reasons for giving up the exclusion of Ihcm from 

 the general series to which they may be considered as 



belonging, and we think most chemists will be inclined to 

 agree with him : — 



" The division of carbon compoimds into two great 

 groups of fatty and aromatic substances, which has found 

 favour of late years, has not been adopted. It appears 

 to have arisen from the comparison of single substances, 

 and cannot be sustained, I believe, if whole series are 

 contrasted. It is now placed beyond doubt that in each 

 homologous series of carbon compounds the properties 

 (physical and chemical) of the successive terms undergo 

 from first to last a progressive modification, and there is 

 every reason to believe that in like manner the successive 

 terms in each isologous series undergo a progressive 

 modification. At present we are not acquainted with a 

 single complete homologous or isologous series, so that it 

 is difficult to draw conclusions ; but to judge from the 

 evidence at our disposal it appears highly probable that 

 the modification in properties from term to term of each 

 homologous and isologous series is of so gradual a cha- 

 racter that continuity may be said to exist throughout. 

 If so, it is as little possible to divide carbon compounds 

 into two great groups as it is to draw a line which shall 

 sharply divide so-called inorganic and organic compounds; 

 that such a division appears possible at present is simply 

 the consequence of the number of links which are still 

 missing in the chain of facts." 



While speaking of certain innovations which Dr. Arm- 

 strong has introduced into his book, the substitution of 

 the term " unit weight " for combining or atomic weight 

 should be noted : the term certainly has the advantage of 

 being free from all theoretical significance ; but if the 

 term citom is objected to, the term combining ivi-ight^ 

 already in common use, would, we should have thought, 

 so nearly have expressed Dr. Armstrong's meaning as to 

 save the necessity of introducing a new term. The 

 general arrangement of the book is clear and simple. 

 The first chapter deals with the methods of organic 

 analysis ; and should any student be so unfortunate as not 

 to have the opportunity of learning from experiment how 

 organic bodies are analysed, certainly if he reads this 

 chapter he will be well able to picture to himself the kind 

 of way in which the determinations are made. The 

 explanation of the use and meaning of formula: naturally 

 follow the determination of the data on which they rest. 

 The following caution to students is not uncalled for, and 

 cannot be too strongly impressed upon them. The author 

 says, speaking of rational, constitution.1l, and structura 

 formula; : '' The use of these terms seems to imply, how- 

 ever, that such formulae express the constitution or 

 structure of the bodies to which they refer ; but we must 

 guard ourselves most carefully against this impression, 

 since, hypothesis aside, we possess no real knowledge as 

 to the internal constitution of chemical compounds, or of 

 the mode of arrangement of the atoms of which bodies 

 are presumed to be made up ; and although rational 

 formula; may represent the approximate constitution of 

 chemical compounds, yet in the present state of our 

 knowledge it is advisable to regard them simply as con- 

 densed symbolic expressions of the chemical nature and 

 mode of formation of the compounds represented ; they 

 enable us, so to speak, to decipher at a glance the 

 chemical history of compounds." 

 The second chapter is devoted to the classification of 



