Chemical lecture experiments . ll size, inserted in rubber stop-pers. Platinum electrodes, whenused for this decomposition, are at-tacked by the nascent chlorine. The addition of small quantitiesof sodium chloride to the hydro-chloric acid used in the experimentdiminishes the capacity of the liquidfor the absorption of chlorine. Con-centrated hydrochloric acid is satu-rated with sodium chloride and thesaturated liquid used in the elec-trolytic apparatus. Both stop-cocksbeing open, sufficient acid is pouredinto the bulb to rise in the two armsto within 2 cm. of the current from s
Chemical lecture experiments . ll size, inserted in rubber stop-pers. Platinum electrodes, whenused for this decomposition, are at-tacked by the nascent chlorine. The addition of small quantitiesof sodium chloride to the hydro-chloric acid used in the experimentdiminishes the capacity of the liquidfor the absorption of chlorine. Con-centrated hydrochloric acid is satu-rated with sodium chloride and thesaturated liquid used in the elec-trolytic apparatus. Both stop-cocksbeing open, sufficient acid is pouredinto the bulb to rise in the two armsto within 2 cm. of the current from six cells of a bi-chromate battery is then conductedthrough the liquid for half an hour,leaving the stop-cocks open. Whilethis operation as a rule should be be-gun before the lecture, the difference in the evolution of gases from the two poles forms an inter-esting experiment for showing the solubility of the end of half an hour the liquid in the arm of theelectrolytic apparatus over the positive electrode will have. Fig. 46 96 CHEMICAL LECTURE EXPERIMENTS become saturated with chlorine, and by closing both stop-cocks it will be found that the two tubes fill with gas atnearly the same rate. The volume of hydrogen will proba-bly be somewhat greater than that of chlorine, though if thestop-cock is carefully opened and the liquid allowed to risein the hydrogen tube to the level of the liquid in the chlo-rine tube, after 20 or 30 cc. of gas have collected, the vol-umes of the gases will increase with much greater rings are advantageously placed on the arms about15cm. below the stop-cocks, and the actual measurement ofthe evolution of the gases begun when the liquids have beendepressed to this level. A piece of white paper held behind the tube containingchlorine will show the green color of the gas. On Openingthe stop-cock the hydrogen may be ignited as it issues fromthe tube, and a piece of iodo-starch paper is instantly turnedblue when held in the gas
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