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INDUSTRIAL A N D ENGINEERINCT CHEMISTRY
When the zeolites were treated only a few times (less than four) with the more dilute acid and alkali brine solutions, it was possible to bring them back to normal behavior and general activity by treatment with increased amount of brine solution of correct H-ion concentration. To allow the zeolite to stand in contact with the brine solution was also beneficial. Such was not true with the zeolites that were revivified with brine solutions contain11000 ing the higher concentrations of acid and 10000 alkali. 2 Figure 3 shows the &o capacity of each of the B zeolites after the four 8000 treatments with t h e $ modified revivifying \? 7 0 0 0 solutions. It must be k. borne in m i n d t h a t 1 where the zeolite shows 4 a decrease in capacity $' 5000 a t the end of the fourth Q $4000 r u n t h e decrease in capacity continues for 3000 t h e following runs. 1 2 3 4 5 Figure 4-Successive Runs Revivifying The mineral eventually Solution Containing 0.1 P& cent Acid shows no base-exchange power. The highest capacity synthetic zeolite sold for present-day use in household or laundry softeners is the most sensitive to changes of hydrogen-ion concentration in revivifying brine solutions. From the results obtained it is seen that the decrease in base-exchange power is not directly proportional to the amount of acid or alkali present. The decrease in baseexchange power, even with acid and alkali concentrations of 1 per cent was far greater than could be accounted for by the solvent action on the zeolite. Mineral 111, however, showed a small loss in weight due to dissolving, and a higher baseexchange power. The natural, processed minerals were not so sensitive to a change in hydrogen-ion concentration as were the synthetic zeolites. All the synthetic zeolites were materially affected by the hydrogen- and hydroxyl-ion concentrations. Mineral I11 behaved in an excep/ / 000 tional manner when /0000 its capacity was inP creased, and the general behavior of the 9 000 B mineral was better in $0000 every respect. This $ z e o l i t e was not so 47000 s e n s i t i v e t o slight change of H-ion conB$ 6 0 0 0 c e n t r a t i o n s as the 4 5 000 other, but the changes were all for a better b f u n c t i o n i n g of the 9 4 000 aeolite. Three s y n t h e t i c 3 000 zeolites manufactured 1 2 3 4 5 Figure &Successive Runs Revlvif InB by precipitation procSolution Containing 0.1Pkcent Na& esses, having similar chemical composition, show the extremes in their behavior on revivification. From an economic standpoint it appears very important to take into consideration the hydrogen- and hydroxyl-ion concentrations of the water in the selection of a base-exchange material for a water softener. As previously shown, mineral I can only be used with a slight variation of the H-ion con-
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Vol. 18, No. 12
centration of the water used for preparing the revivifying solution, a hydrochloric acid or sodium hydroxide concentration of one part in ten million being sufficiently great to decrease materially the base-exchange power of the mineral and eventually completely destroy this property of the rnineral. This is doubtless true for any acid or alkali. It is known to be true with sulfuric acid. The results show that a specific water should be softened by a special zeolite in order to get the proper revivification, or else the hydrogen-ion concentration of the revivifying solution should be properly adjusted. Conclusion The particular mineral which is to be used on a particular water should show by a test an H-ion concentration within the safe limit set by the above curves, when made up into a 5 per cent salt solution. Should the water be so acid or alkaline as not to give a safe H-ion concentration, either a mineral with a safe range should be used or else means should be provided for adjusting the acidity or alkalinity of the revivification solution. Partially completed work in this laboratory indicates that the minerals show similar sensitiveness to the water which is being softened. In this case it is imperative that a mineral be chosen to suit the water, since it would obviously be impossible to adjust the H-ion concentration of the water to be softened.
A Modified Weight Buret' By G . Frederick Smith U N I V B R S I T Y OF ILLINOIS, URBANA, ILL.
HE usual design of weight buret has numerous shortcomings, such as lack of proportions which adapt it to ready suspension from the usual supports provided in popular makes of balances, troublesome stoppers above and below, provision against moist contacts a t stoppers, over or under capacity, ..etc. The accompanying illustrations are self-explanatory in m e e t i n g t h e s e difficulties. The drawings are half actual size, the bulb capacity being betwem 30 and 40 cc. The lower stopper readily provides for replacement without moistening the contact due to a partialIy suspended drop at the exit orifice. The constriction in the neck with calibration permits of charging with a given solution to a given weight, which facilitates repeated weighings using the same reacting solution and at the same time aids in keeping top ground surface dry. The wire suspension from supports placed symmetrically permits a free swinging positiofl with the bottom cap clear of the balance pan. This apparatus should be made of Pyrex glass to gain the desired sturdiness. The improvements in the proposed design of weight buret are due to Paul Anders, University of Illinois, glass-blowing technician. 1 Received
October 22, 1026.
