A BLYCERIIU-SEALED MECHANICAL STIRRER
THE use of the merrury-waled mechanical stirrer, akhough almost unirersnl in chemistry lnboratories, has seveml climdvnntnges. Mercury is nlwnys a nuisance to handle, and exposure to it is detrimental t o n person's 1imlt.h. I:urthermore, for chemirnl renctions in which halogens or halogen acids nre prcsent the mercury usunlly reacts with the halogens or hnlogen acids. In onler to avoid the use of mercury a
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glyrerinaenled mechnnicnl stirrer has been devised, whirh may he made from parts rrntlily ohtainnhlc in any chemical 1aborntory-n piece of g l : tubing ~ and three rubber stoppers, na shown in the figure. Stopper R is size 4 or 5 nnd stopper C of the proper size to fit 6he flnsk. Tubing D is fittrd tightly to s t o p p e n R nnd C nncl estcndecl 5 mm. nlwve f?, forming a wnII to prevent n c c m of glycerin to the stirrer shrift. Stopper A is onc size sm:~llerthnn stopper f? and is bored to u depth of ahout T mm. ~vithn cork borer whose diameter is about 3 mm. Inrgrr than thnt of tubing D. The corn is cut out with :I pair of wiswrs. The stirrer in p a d through D nnd then through the tightly fitting stopprr A for such u clisti~ncethnt when stopper A rests on stopper R the stirrer ir nt the dcsiml Irvrl in t h r flnsk. The s~~rfnccs betwecn stoppers .4 and R are luhrirntd nntl senlrul with glycerin. This wnl hns srvrrnl ndvnntngrs over u glycerinluhricntccl sleeve of n ~ h b r rtubing. It is not nweswry to find n ~ b b e rtubing and glnss rod of the proper size for a close fit, and there is lew clnngcr of contnminntion of the reaction mixture with glycerin. I t hns the aclvantnge over the reservoir type of glycerin-wnled stirrer in that it is simpler and less cumbersome to mnnipulnte. The same seal may be u m l for flasks of different nizes simply by interchanging stopper C to fit enrh flask.
