ILYDUSTRIAL A,VD EXGISEERING CHEMISTRY
1190
an organism, Bacterium brassicae, which did not form any gas. Hennebergs states that the carbon dioxide production may a t first be due to the respiration of the plant cells, but later the yeasts play a more important role. Peterson, Fred, and their a ~ s o c i a t e s ~ ~have J ~ J ~isolated a large number of mannitolforming bacteria from sauerkraut. These bacteria convert 20 to 25 per cent of the glucose and other sugars into ethyl alcohol and slightly higher percentages of the sugars into carbon dioxide. It is therefore not necessary to have yeasts in sauerkraut in order to have gas and alcohol production. A fact clearly seen in all the graphs is the close parallelism of gas and acid production, especially in the earlier stages of the experiments. Since acid production in sauerkraut is attributed to bacterial activity, the logical conclusion can be reached that gas production is also a bacterial activity. Further proof for this conclusion lies in the fact that with the rapid increase in gas and acidity in Experiment IV there was a simultaneous rapid increase in the number of bacteria. I n order to determine how many of these bacteria produced gas, 15 colonies from the plates of each sample of juice were picked into tubes of sterile, glucose yeast-water medium; in all 105 colonies were picked. The tubes were sealed with sterile melted vaseline incubated a t 28"C., and observed from day to day for turbidity and gas formation. If the vaseline plug was pushed u p they were recorded as gas-positive. If the vaseline remained a t the surface of the liquid and there was no apparent leakage of gas, they were callqd negative. After 8 days of 18 14
J . Biol. Chem., 41, 273 (1920). Ibid., 64,643 (1926).
Vol. 20, s o . 11
incubation all the cultures which showed no gas formation were reinoculated into fresh, sterile medium, plugged as before, and incubated a t 28" C. for 5 days. Twenty per cent of the 105 cultures showed gas formation. Three-fourths of those cultures showing gas were obtained from the samples taken within 4 days after the cabbage was packed in the barrel. Even a higher percentage of gas-forming bacteria was reported by Priem, Peterson, and Fred" in commercial sauerkraut which had been fermented a t temperatures below 10.5" C. These investigators found that 70 per cent of the bacteria produced gas. I n the light of these data it seems justifiable to conclude that bacteria are the primary agents responsible for the production of the gas in sauerkraut fermentation. Summary
1-The gas evolved during the formation of sauerkraut is almost 100 per cent carbon dioxide. 2-Most of the gas formed is given off within 40 to 160 hours after the cabbage is packed into the container. 3-Since there is a very close relationship between gas, acidity, and numbers of bacteria, the conclusion is reached that the gas production is due t o . bacterial activity and not to yeast growth or plant-cell respiration. 4-The fermentation of cabbage is much quicker at higher temperatures than a t lower temperatures. +Washing the cabbage before cutting and packing has an apparently favorable effect upon the flavor of the sauerkraut.
Dufton Distilling Column for Preparation of Absolute Alcohol' W. A. Noyes UNlVERSITY OR ILLINOIS, U R B A N A .
I
T HAS been shown that, with a suitable apparatus, very
nearly absolute alcohol may be obtained by means of calcium chloride.2 A simplified apparatus, including a Dufton distilling ~ o l u m n ,has ~ now been devised. The alcohol is heated in a 15-liter copper boiler, A , by means of a steam coil of galvanized iron pipe, B , 18 mm. in diameter, using steam under a pressure of 6 kg. per sq. cm. (90 pounds). The distillation is controlled by a valve which regulates the rate a t which the condensed water runs away. Description of Apparatus
The Dufton column consists of an inner brass tube, C, closced a t both ends, and of 21 mm. outside diameter. Around this is wound an annealed copper rod, D, 6.5 mm. in diameter, leaving the successive spirals 2 cm. apart. The spiral is inserted in a copper tube of 35 mm. inside diameter and fits so closely that it was necessary to file flat places on the outside of the spiral a t frequent intervals to permit the solution of calcium chloride to flow downward more freely. The column is 140 cm. long. It is soldered to the bottom of a brass reservoir, E , 10 cm. in diameter and 30 cm. long. A short piece of brass tubing, E , 20 mm. in diameter, passing through the bottom of the reservoir, delivers the vapors of alcohol, coming from the top of the column, immediately beneath the center of a conical, perforated diaphragm, upon 1 Received
2 3
June 13, 1928.
Noyes, J Am. Chem. SOC.,46, 857 (1923). Dufton, J . SOC.Chem Ind., S8, 45 (1919).
ILL.
which the anhydrous calcium chloride was placed. A short tube a t the side of the reservoir a t its bottom is connected by means of rubber tubing and a short U-tube, G, with a similar tube a t the top of the column. This makes it possible to see the character of the solution of calcium chloride running from the bottom of the reservoir down the column. A ooil of small copper tubing, H , in the top of t h e r e s e r v o i r , through which water is allowed to run very slowly, causing the condensation of a small amount of alcohol, controls the downward flow of the solution. From the top of the reservoir a tube of block tin connects with a worm, I , for the condensation of the alcohol. Operation
Put in the boiler 1500 cc. of alcohol recovered from the last distillation; distil 500 cc. and return this through the reservoir a t the top. Put 10 liters of ordinary alcohol into the boiler, and 800 grams of calcium chloride into the reservoir a t the
Soveinber, 1928
INDUSTRIAL B N D ENGIiVEERI-YG CHEMISTRY
top. Pour 200 cc. absolute alcohol on the calcium chloride. ,4110~the cooling mater running through the small coil in the top of the reservoir to drop slowly, about 50 cc. a minute. Distil 3 liters at the rate of 2 liters an hour. Put 500 grams of calcium chloride into the reservoir, distil 3 liters, and again add 500 grams. Then distil till the distillation ceases because of the separation of calcium alcoholate in the boiler. This should gire about 9500 cc. of alcohol of 99 per cent by weight. The apparent loss of 500 cc. is due chiefly to the decrease in volume from the removal of water. Allow the apparatus to cool for half an hour, put 1200 cc. water in the boiler, and distil till the thermometer a t the bottom of the Dufton column registers about 110" C. This
1191
should give about 1500 cc. alcohol of 96 to 98 per cent, to be used in the next operation. Draw off the solution of calcium chloride from the bottom as soon as the distillation is completed. By distilling the 99 per cent again in a similar manner, the strength may be brought to 99.7 per cent, which is a t least as strong as that usually obtained with lime. By distilling more slowly it is also possible to carry the strength considerably above 99 per cent in a single distillation of ordinary alcohol. I n one case a small amount of alcohol of 99.95 per cent was obtained. It is more practicable, however, to complete the removal of the last portion of the water with active lime as described in the earlier paper.2
Hydrogen-Ion Control in Water-Softening' John R. Baylis DEP4RTMENT OF
PUBLICW O R K S , BUREAUOF EXGIXEERISG, CHICAGO, I L L
w
A knowledge of the pH of the water through the differATER-softening hato the usual method of exent stages of the softening process enables the most p r e s s i n g hardness which is made rapid adefficient results to be obtained in a plant where lime is based u p o n the parts per vances within the> used for softening. million of calcium carbonate. past twenty years; yet it i\ The approximate saturation equilibria of calcium The pH of this solution is almost in its infancy. Reand magnesium carbonates have been established. sults a t existing plants indiabout 12.35. If carbon diThe concentration of magnesium carbonate at saturacate that it would be economy oxide is added, the pH and tion equilibrium is much higher than calcium carto soften by chemical precipialso the concentration of calbonate for a given pH. Most natural waters contain tation practically all waters cium in solution will be resome magnesium carbonate and this throws the saturah a v i n g a h a r d n e s s of 100 duced by precipitating caltion equilibrium somewhat higher than the curve for p a r t s p e r million or more. cium carbonate. This decalcium carbonate. I n fact, it would often be crease continues as carbon Magnesium begins to precipitate as the hydroxide economy to soften when the dioxide is added until the when the pH is increased above 10.3. Where the maghardness is less than this fighardness reaches a minimum nesium occurs largely as the carbonate, it can be reure. It is believed that this of. about 13 p. p, m. a t a p H duced to about 3 p. p. m. of magnesium by increasing includes approximately oneof about 9.4, provided suffithe pH to about 10.8 with calcium hydroxide. fourth of our public water cient time after the addition The maximum softening possible for waters consupplies. The point to which of the carbon dioxide is altaining both calcium and magnesium carbonates is it is economical to soften delowed for equilibrium to be to add lime until the pH is about 10.8 and then prepends on the uses of the water established. This, of course, cipitate the calcium by converting it to the carbonate. and the cost of softening. is well known to most water I t is better to recarbonate at two or three stages of The main constituents of chemists. Continued addithe process than to attempt to recarbonate at only one water that make it hard are tion of carbon dioxide inpoint. the compounds of calcium and creases t h e hardness and m a g n e s i u m . Several comlowers the DH. Almost as pounds of these elements may be present, but for the majority much 'calcium can be thrown back into sofution in the biof the fresh waters the bicarbonates occur in greatest quanti- carbonate form as was present in the saturated solution of ties. Factors influencing the precipitation of the carbonate calcium hydroxide. It is evident that the minimum point of calcium and the hydroxide of magnesium really determine of solubility, which occurs a t a pH of about 9.4, is of great the degree of softening that may be accomplished, for other importance in water-softening. salts of these elements as may occur in the water are usually Magnesium differs from calcium in that the hydroxide is converted to these salts in order that precipitation may be much less soluble than the carbonate. The saturation equieffected. For example, should a large amount of calcium librium of magnesium hydroxide is about 3 p. p. m. of magsulfate be present, it is customary to add sodium carbonate nesium at a p H of about 10.6, Greenfield and Buswel12 find to the extent that the sodium will replace the calcium in that the precipitation of magnesium as magnesium hydroxide combination with the sulfate, forming sodium sulfate and is complete a t a pH of about 10.6 and the precipitation of calcium carbonate. Sodium hydroxide may be used instead calcium carbonate is complete a t a pH of 9.5. Adding carbon of the carbonate when there is already sufficient carbon diox- dioxide the concentration of magnesium in solution increases ide in the water. as the pH decreases until considerable magnesium is present Saturation Equilibria of Hydroxides and Carbonates of as the bicarbonate. At a pH of 8.8 and temperature of 23" C. about 240 p. p. m. of magnesium will be found in solution Calcium and Magnesium when equilibrium is established. The hardness of a saturated solution of calcium hydroxide It is evident that the most magnesium can be precipitated at 20' C. is somewhere near 2200 p. p. m. This is according from hard waters by converting it to the hydroxide, and that Presented before the Division of Water, Sewage, and Sanitation the most calcium can be precipitated by converting it to the Chemistry a t the 75th Meeting of the American Chemical Society, S t Louis, &'IO, April 16 to 19, 1928
J A m Chem S O C 44, , 1435 (1922).
