A Convenient Method of Labelling Ampoules During Kinetic Investigations

Common techniques used in following kinetic investigations often involve the use of large numbers of ampoules containing individual aliqoots which are removed at time intervals. There are various brands of glass pencils and water insoluble inks available but i t is often difficult to find with certainty a. satisfactory one for use in constant tem~erttture baths containine orzanic solvents or oil. .~ .. .. ~ ~

A vrr? c o ~ ~ r ~ c ~ r i w t nlethrd uf lubrllin~ the ~ m p o d e i involver thr uic of ndured plasric brad,. .4 w i l d h length of ~ l i n c~ppr r wire cn. 3 in. fur a I-vnl ar~qrut.lr) is twisrrrl tightly r u ~ ~ n d the ncck ui the ampwlr, a mlurwl t m d is thrrnded thruugh unr end of the wirc and the end* hen closed by twi3ring them together tighclv, but lr.tving dfirient length so that the wires form a loop.

This loop of wire is convenient for suspending the ampoule in the bath, e.g., by threading i t over a hook in a piece of hesvy gage wire or glass rod. I t can also be used for withdrawing ampoules out of a. bath by a similar method. Colored beads are able to be identified quickly in a bath containing many different "runs" and the method is capable of infinite variations, e.g., each run could have a basic color, and an additional bead could be added to those samples which have special treatment, e.g., a sample which is removed and frozen overnight and then returned to the bath, or an infinite time sample which in slow runs might he put in a bath of higher temperature than that in which the kinetics are being carried out. Each concentration could have a. different color, or each compound, and runs of the same compound and concentration hot at different temperatures could he separately identified, the only limitation being in the variety of heads available. Children's necklace kit sets m d jug beads are the cheapest and offer the most variety, hut cheap necklaces could he unthreaded and even such identifying objects as domes, brass washers of various sizes and insulating beads have been used. Glass beads have been found unsatisfactory as they break a t high tem- peratures and often become diswloured or bleached. Plastic beads however are cheap and can he used inperpetuity since they are resistant to heat and solvents. This method has been used without confusion for carrying out up to 80 different runs simultaneously.

380 / Journal of Chemical Education