260 



SCIENCE 



[N. S. Vol. XXXVI. No. 922 



the structural formulEe unknown, but in 

 most eases the empirical formulae are still 

 in doubt. For instance, the formula for 

 abietic acid has been generally accepted as 

 C20H30O2, but Mach in his dissertation on 

 the acid gave to it the formula CigHogO.. 

 Absolutely nothing is known of its chem- 

 ical constitution. 



Various theories have been advanced con- 

 cerning the relationship between the resins 

 and terpenes. What evidence there is may 

 be briefly stated. The fact that the alde- 

 hydes in the presence of alkalies change to 

 resinous matter was presented by Wiesner 

 in what may be called the reduction theory. 

 Wiesner^ assumed that the resins are 

 formed from the carbohydrates, or, speak- 

 ing more specifically, from the starches by 

 a process of poljonerization and reduction. 

 It is perfectly evident that Wiesner 's the- 

 ory is not applicable in all cases. The pine 

 family, for instance, contains a minimum 

 amount of starch, yet it is the richest of the 

 resinous species. Wiesner was aware of 

 this fact and assumed that in the case of 

 the pine family the resins were formed 

 through the action of gallic and gallo-tan- 

 nic acids. 



While the starch theory has certain facts 

 in its favor, there are, on the contrary, 

 serious objections to it. It would seem not 

 only strange, but also diametrically opposed 

 to general chemical laws, that plants should 

 proceed to build up the complex starch 

 molecule and then break it down again into 

 the resin and finally into the terpene mole- 

 cule. Of course, it must not be forgotten 

 that the sugars belong to the aldehydes and 

 tend to form resinous substances when 

 treated with alkalies. They are, however, 

 by no means as readily converted into 

 the resins as the simpler aldehydes. One 

 would naturally expect that if the resins 

 are formed by the aldehyde reaction they 

 -Centr., 1865, p. 756. 



would proceed from the simple rather than 

 from the complex aldehydes or sugars. 



One of the first comprehensive works on 

 the formation of the resins from the alde- 

 hydes was presented by Baeyer. He ob- 

 tained several synthetic resins by the alde- 

 hyde condensation reaction, but an exam- 

 ination showed that they were unlike any 

 of the resins found in nature. In each 

 case the molecule seemed to be extremely 

 complex and no attempts were made to 

 determine the structure or the size of the 

 molecule. Kronstein, following out the 

 work which Baeyer had begun, presented 

 constitutional formulse for these aldehyde 

 resins in a very unique but entirely em- 

 pirical way. He assumed the resin mole- 

 cule to be a complex benzene ring or per- 

 haps several superimposed rings joined 

 with either hydrocarbon, methoxyl, ethoxyl 

 or carboxyl radicles, and gave the graphic 

 formulae for them. Of course such struc- 

 tural formulse are interesting, but needless 

 to say they are not based on experimental 

 data. 



In the starch explanations of the forma- 

 tion of the resins in plants, it must be as- 

 sumed that the resins are formed by first 

 building up the complex starch molecules 

 from the simpler aldehydes, and then 

 breaking them down again into the resins 

 and terpenes. So far as can be ascertained 

 there are no experimental data in favor of 

 this theory. If, on the contrary, we assume 

 that the resins are built up from the simple 

 aldehydes, the process is more logical, as it 

 only requires two steps, namely, polym- 

 erization and reduction, instead of three 

 distinct steps as indicated in the following 

 simple diagram: 



Aldehydes >Resin ^Terpenes 



(Formaldehyde) 



While the above theories have many 

 points in their favor, there is another 



