NOTES. Er’y).o~s .g~i>.ifig./;vnt Use of Cork Sfobjers iiz Qiuz izfiiafitie Exti-actioiis a i f h Acetaiie.--The iise of cork stoppers for quantitative extractiotis is geuerally considered to be unobjectio:iable, but tlint such is not t h e case was recently called to my attention during a series of rublier aiialyses. T h e ordinary method of dc-termining t h e a c c t ~ i l ee s t r a c t n.itli t h e use of a Soxhlet extractor a c d cork stoppers w a s beitig i;sed, ]Jut it was found al1113:jtimpossible to reiiiove all the soluble extract although tlie extraction was coutinued for 90 hours. A n exa:iiitiatioii of t h e cork stoppers furnished a ready e s ~ ~ l a n a t i o n .X white resitious matter liad separated out in t h e cracks of the cork, aiid a ring of tlie same material hat1 formed on the stopper and also on the glass \\.liere the tlvo came in contact. It was evident that soiuble :]latter was 1)eiiig extracted. I he amount of this soluble matter \vas determilied by cutting u p a cork weighing 4. I S grams, placiiig it i n an extractioii thimble and extracting with acetone for five hours. o.wSo grams of a white resinous material was obtained. I t is not coiisidered that t h e cxtraction was complete \)tit it i1n.i procexlecl far eiiouqh for the purpose of t!ie experiment. T h e iiiiportance of this matter, ebpecially i n rublier aiialyses where the total weight of extract (in P a r a rubber) seldoni exceeds 0.06oo g r a m s can readily be seen. I t is t r u e that cutting the cork into siiiali pieces :is in t h e above experiment made the conditions for the extraction of soluble matter more favorable tliaii in an analysis, but tlie porosity of the cork is so great that even under actual conditions a very considet able aiiiouiit would lie dissolved. Furthermore ail estractioii u ~ u a l l ycontinuts for a longer time than above and extraction proceeds from two stoppers instead of oiie. Disregard of this matter is probably one of tlie factors whicli are responsible for the great discrepancies noted between the results of differe n t chemists in t h e analysis of rubber. T h e remedy obviously lies i n t h e use of ground glass cont~ectionsbetween flask aiid extractor and e x tractor and condenser. ED\\.. A. B A R R I E R . Ziicq
I \
LABORATORIES O F THE
.kSSOCIlTED
F I R EI N S . COS., Boston, Mass.
WACTORY M V T U h L
Otfo Dinirotlt’s Paper: ‘‘Behavior of Diazoiiizinz Conipounds Towards Ketoiiic nizd Ezolic Desmotrojhy” .-In a recent paper,‘ bearing t h e above title, Prof. Otto Dimroth describes t h e behavior of a number of ketonic a n d enolic compounds towards p-nitrobenzenediazonium hydroxide. The I
I
enolic compounds yield azo derivatives HOC : CN : NR, whereas t h e k e tonic compounds fail to react. Dimroth discusses t h e various possible HON : methods of formulating t h e reaction a s follows : ( I ) OCCHR’
+
Ber. 40, 2404.
