September, 1923
INDUSTRIAL A N D ENGINEERING CHEMISTRY
EFFECT OF ALUMINIUM SULFATE
the treated sludge a t its optimum pH value is shown in Fig. 4, the best result being obtained a t the boiling point of water. A still further increase in relative filtering efficiency can The seasonal changes in sludge treated with aluminium be obtained by adding 1 pound of aluminium sulfate to every 50 gallons of waste sludge and adjusting the pH value to 4.4. sulfate, acidified to make pH = 4.4 and heated to 160" The reason for the shift in optimum pH value to 4.4 may be F., are shown in the top curve in Fig. 1. This treatment raises explained by the necessity for the sludge to carry a negative the increase in relative filtering efficiency to a grand total electrical charge in order to co-precipitate the positively of about 4000 per cent. The problem of dewatering activated sludge a t all times of charged alumina. Fig. 3 shows that the optimum efficiency is obtained a t 4.4,both for cold and heated sludge contain- the year may, therefore, be considered as solved for the cliing the aluminium sulfate. The effect of temperature upon mate of Milwaukee.
Effect of Deaeration of Natural Waters on t h e Carbonate Equi li bri urn' By D. H. Jackson and J, R. McDermet ELLIOTT Co., JEANNETTE, PA.
N VIEW of the rather
I n this paper it is shown that deaEration remoues all free carbon so that the condensate drains back into the vacuum large volume of literadioxide and decomposes about 35 per cent of the bicarbonate present, chamber and falls with the ture on aggressive carmost of it being precipitated and a small amount remaining in water from the spray heads bon dioxide and hydrogensolution as calcium carbonate. The percentage bicarbonate reover a series of cascade pans ion concentration of natural moued increases slightly with increase in concentration of &carinto the storage space in waters, it was considered bonate. The p H calues are changed by deazration from slightly an appropriate and interthe bottom of the chamber. acid to a fairly high alkaline calue. the change aueraging p H 2.5. esting problem to study the The water level in the effect of deaeration of such chamber is regulated by waters on these factors. Experiments in this field should be a float-controlled valve. The vacuum is produced by an especially significant a t this time owing to the growing com- ejector of the steam jet type or by a motor-driven air pump mercial interest in the application of apparatus for removing connected with the condenser. I n the former case an auxdissolved gases from water in systems where it is desired iliary condenser is used to recover the heat from the steam to prevent corrosion. The principal reason for removing dis- and the air extracted from the vacuum chamber passes solved gases is to eliminate the dissolved oxygen, which is through a vent to the atmosphere. the chief cause of corrosion of iron and steel by water. HowWater treated as above in practically all cases is delivered ever, the carbon dioxide content should by no means be with an oxygen content of from zero to a trace, a trace meanneglected, and the experiments recorded in this article were ing less than 0.02 cc. per liter as measured by the Winkler run with the idea of determining the change in hydrogen-ion iodimetric method. concentration and the extent of bicarbonate removal when CARBON DIOXIDE TESTS the free carbon dioxide in natural water is removed by complete deaeration. The water on which the carbon dioxide tests were run was the regular water supply of a power plant which takes water DEAERATION PROCESS from a small stream about one mile north of Jeannette, Pa., A complete description of this apparatus from both and is characteristic of the water of the surrounding section. theoretical and practical standpoints is given by McDermet.2 The water is used in the power plant without being filtered The deaerator t o which the writers had access for running or otherwise treated than by the deaerator. Tests were these tests is of the same type as is being extensively in- run at different seasons of the year, so that the conditions stalled a t the present time to prevent corrosion in power could be varied as much as possible. A complete mineral plants and hot-water service systems. analysis of this water might be of interest in connection with Before entering the deaerator, water must be heated to the experimental results of this paper, and a representative a minimum temperature of 160' F. The apparatus may analysis is given in Table I. be designed to handle water a t any temperature from 140"F. up to the boiling point. Water enters the deaerator through TABLE I-ANALYSIS OF WATER TESTED a spring-loaded valve and passes through spray heads into PARTSPER MILLION PARTS PER MILLION Calcium 29.6 Chlorides 4 ;97 a vacuum chamber. The spring-loaded valves tend to keep 5.16 Carbonates a s COa 71.4 Magnesium a constant pressure on the spray heads with change in water 21 66 Iron oxide 4.62 Sulfates R R1 Alumina 3.10 Silica rate. The hot water entering the vacuum chamber is subSodium 2.34 Organic matter 28.00 jected to a process of explosive boiling a t the expense of the Ammonia Trace Suspended matfer 16.7 Nitrites Trace Total solids 186.20 heat it contains. The vacuum is regulated so that enough Nitrates 1.1s pH = 6.8 maximum, 5.8 minimum water is boiled to reduce the temperature of the water about 22' F., as this gradieht has been found to produce perfect I n connection with the test of deaeration on carbon dioxide deaeration. The steam produced in the boiling process is drawn off into a small surface condenser which is cooled removal, determinations of free carbon dioxide, bicarbonate, by the water going to the heater. The condenser is located and carbonate were all carried out by t'itration, using the methods and precautions suggested by Johnston. The 1 Received April 12, 1923.
I
2
Mech. Eng., 44. 273 (1920).
* J. A m . Chem. SOL.,88, 947 (1916).
INDUSTRIAL AND ENGINEERING CHEMISTRY
960
free carbon dioxide was titrated with 0.02 N standard sodium carbonate. This solution was carefully bottled and stored in such a way as to prevent it from coming in contact with the atmosphere. The bicarbonates and carbonates were determined by titrating with 0.02 N sulfuric acid, according to the methods and precautions mentioned above. As a check on the results, the total carbon dioxide was determined on many of the samples by measuring the volume of gas liberated by sulfuric acid in a Van Slyke apparatus and also by displacing all the carbon dioxide with acid, boiling, and determining gravimetrically by absorption in a Flemming bulb. p H DETERMINATIONS The pH determinations were made with the aid of a hydrogen electrode against a mercury calomel cell and other standard equipment, which was periodically standardized against buffer solutions. Samples from the deairator for p H determinations were placed in a beaker covered with a rubber diaphragm with three holes through it to accommodate the hydrogen elect!rode, the salt bridge of the calomel cell, and a motor-driven stirring device. Before the sample was introduced into the covered beaker, the latter was filled with hydrogen by displacement of water. The sample was then forced into the covered beaker by hydrogen pressure, entering through the hydrogen electrode without having had any chance to be polluted by the atmosphere. It might be suspected that the atmosphere of hydrogen over the sample while it is being stirred would have an appreciable effect upon the concentration of the other dissolved gases. This would doubtless be true if there were dissolved gases present, but both chemical and physical methods have been used in making determinations, and results are usually zero, or if any is found, the quantity is so small as to be negligible. In measuring the p H value of the raw water, samples were placed in an open beaker and run until the potentiometer reading was constant. Such results are probably slightly higher than they should be, owing to displacement of some of the carbon dioxide in solution by hydrogen from the electrode. However, the sample was in direct contact with the atmosphere while the determination was being made and equilibrium is supposed to exist between the two. DETERMINATION
OF
TOTAL CALCIUM
The determination of total calcium was made on both raw and deaerated water to find out how much calcium was precipitated by deaeration. Results were obtained volumetrically by titrating the calcium oxalate with potassium permanganate and checked gravimetrically by weighing the oxide.
COMPARISON OF RAW AND
DEAERATED
WATER
Throughout the experiments for the comparison of raw and deaerated water, samples of raw water and of dea6rated water were taken at practically the same time, the former being taken from the cold-water line to the heater and the
latter from the deaerator discharge. I n collecting samples from the deaerator, care was taken that there was no chance for pollution by contact with the atmosphere.
RESULTSOF TESTS All samples of water tested are on the acid side of neutrality, as shown by p H value from 6.85 downward. After deaeration the p H value ranges from approximately 8.8 to 9.5 and a good color change is always produced when phenolphthalein is added. This change is due to removal of carbon dioxide and partial decomposition of bicarbonate. When a sample containing phenolphthalein is stirred with a motor stirrer, it takes from 15 minutes to more than half an hour for the color to entirely disappear. It is observed to fade gradually away throughout the whole time. When the solution is allowed to stand in an open beaker, it takes from 6 to 48 hours for the color to fade away. It is evident, therefore, that it takes considerable time for the atmosphere to put back into the water the amount of carbon dioxide taken out by the deaerator in a fraction of a minute. The results in Table I1 are representative of a large number of tests run as outlined in preceding paragraphs. The complete tests on samples showing the maximum amounts of bicarbonate are included in the table in order to emphasize the facts, as shown by the results, that the percentage removed increases with increasing concentration of bicarbonates. I n Table I1 no results are given for free carbon dioxide in deaerated water, for, as would be expected, free carbon dioxide cannot exist in water with the high pH values which all tests consistently showed on deaerated water. The higher p H values of deaerated water samples are partly due to the removal of all free carbon dioxide and partly to the formation of carbonate from a portion of the bicarbonate. The results show from 4.6 to 6.8 parts per million of carbon dioxide as carbonate in deaerated water. The solubility of calcium carbonate a t 16" being 13 parts per million, which corresponds to 5.72 parts of carbon dioxide per million, it is evident that the solution has become saturated with carbonate and the excess, as indicated by the difference between the bicarbonate content of the raw water and the total carbon dioxide content of the deaerated water, has been precipitated. The difference on either side of the carbonate solubility point and the experimental results can be explained by changes in temperature or by adjustment of equilibrium after the water is deaerated and by the fact that small amounts of precipitated calcium carbonate may remain suspended in the solution. Suspended calcium carbonate was detected in samples of deaerated water by filtering and analyzing the residue. The last sample in Table I1 was obtained from a different plant than the others and is well water. The p H values were determined with colorimetric indicator standards at the source of collection of the samples, and the titrations were run after the samples had been shipped to the laboratory. These analyses gave practically the same results as some of
TAB&& II-RSSULTS OF TESTSFOR CARBON DIOXIDE,PH, Free Raw Water P. p. M.
-BicarbonateRaw
P.p. M.
..
AVERAGE 78 2
Deaerated
P. p. M. 48.3 63.5 46.2 62.4 48.4 60.8 42.5 63.4 66.6 66.9 68.5 64.6
Carbonate Deaerated
P.p. M. 6.4 0.6
6.8 4.6 4.7 6.4 6.3 6.6 6.6 6.3 6.1 6.0
-Total Raw Water
P.p. M.
COaDeaErated Water P. p. M.
88.2 97.6 80.4 95.2 88.3 92.0 74.6 96.2 103.1 105.9 108.8
54.8 61.4 53.1 56.5 53.9 68.4 49.3 60.2 61.9 63.6 66.7
..
Vol. 15, No. 9
AND
TOTAL CALCIUM
-pH-Raw Water 6.70 6.76 6.70 6.70 6.68 6.70 6.67 6.76 6.76 6.75 6.82 6.70
Deaerated Water
9.33 9.28 9.37 9.16 9-19 9.36 9.37 9.27 9.30 9.32 9.39 8.70
-CalciumDeaerated
P. p. M. 26.4 27.9 25.6 -26.0 26.9 26.0 25.0 27.8 28.0 28.4 28.9 27.1
Raw
P. p. M. 30.6 32.4 29.0 31.7 29.3 31.6 28.3 32.3 32.6 33.2 34.1 30.5
INDUSTRIAL A N D ENGINEERING CHEMISTRY
September, 1923
the others, showing just a little less bicarbonate removed than any of the others, which was probably due to changes in the water after the samples were collected. As a theoretical check on the analytical results of bicarbonate determinations in dea6rated water, the following formula, as given by Massink and H e y m q 4 was used to calculate the bicarbonate content: H+ = 6 X
X
961
present in either case as would be equivalent'to the amount of bicarbonate found, showing that part of the bicarbonate is combined with other elements, probably magnesium.
Bicarbonate CO, Carbonate CO,
Hf being the hydrogen-ion concentration and the COz values being expressed in milligrams per liter. A comparison of the calculated results with the experimental results on the different samples in Table I1 are given in Table 111. TABLE111-BICARBONATE EXPERIMENTAL CALCULATED 48.3 50.1 53.5 57.6 4.5 2 ...~
48.1
52.4 48.4 50.8
49.3 80.4 47.0
C02-MG. PER LITER EXPERIMENTAL CALCULATED 42.5 45.2 53.4 59.2 55.5 53.6
56.9 58.5
60.1 62.1
The results check fairly well, considering how much the value of the formula depends upon the accuracy of the pH measurements. The results on calcium in raw and deaerated water show that an appreciable amount is removed by deaeration-not as much, however, as would be expected from the amount of bicarbonate removed. Indeed, there is not as much calcium 4
J . A m . Water Works Assoc., 8,239 (1921).
W
S
F€R MIWON BhMBONWE COz
FIG 1
To give an idea of the relative amounts of bicarbonate removed, a curve is given showing the total bicarbonate present in the raw water, plotted against the per cent removal by deaeration. The per cent removal is found to increase slightly with increase in concentration. It would be interesting to test the effect of deaeration on water with higher bicarbonate content, but it could not be done by the writer, as the laboratory was only convenient to the one power plant where deaerated water was auailable.
Substitution and Addition of Chlorine to t h e Rubber Molecule' By J. McGavack UNITEDSTATICSRUBBERCo., NEW YORK,N Y.
T
The main points in this brief paper are that substitution occurs work done by Peachy.3 HE nature of the refirst in an uncontrolled temperature reaction of chlorine with rubber: In general, d authorities action of chlorine that, practically, substitution is complete before any addition occurs; PracticauY agree, with the with hydrocarbons that the procedure giues a quick method by which the rate of the chloexception of Boswell, that depends upon the temperature, light, and mechanrination of rubber may be determined at any particular time. the rubber hydrocarbon is ical conditions, as well as an unsaturated aggregaupon the nature of the tion of carbon and hydrohydrocarbon itself. Saturated hydrocarbons can only react gen. Boswell4 claims that, instead of having a number with chlorine by substitution. On the other hand, both of double bonds affording an opportunity for the addition substitution or addition may occur in the case of un- of compounds like bromine and chlorine, we have internal saturated hydrocarbons. For instance, the chlorination of linkages between the carbon atoms, thus causing complete toluene may result in entirely different chemical individuals, saturation, and that the formation of double bonds of free depending upon whether the reaction occurs in sunlight, valencies is only brought about when extreme or drastic diffused light, or a t an elevated temperature. In the same treatment is employed. I n any case, it was thought demanner the chlorinated products of ethylene may vary over sirable to study this reaction from the dynamic standpoint. a wide range, depending Primarily upon the conditions under The method (Fig. 1) consisted in passing a definite quantity which the reaction is carried out. In fact, examples of this of chlorine measured by a flowmeter (1) through a cylindrical type are SO frequent and familiar that it is USeleSS to cite vessel exposed to diffused light containing a known quantity further cases. of rubber cement., The effluent gases were cooled by means For this TeaSon it Was thought that 2, dynamic study of of a condenser allowing the solvent to return to the reaction the chlorination of the rubber hydrocarbon should be inter- chamber and were measured by means of flowmeter (2). esting and perhaps indicate the preference for substitution These gases were then washed thoroughly with water to O r addition. Previous workers, such as Gladstone and remove any hydrochloric acid formed, measured by another Hibbert,2 have considered the chlorinated product of the flowmeter (3) ; and finally passed through strong alkali to rubber hydrocarbon from the end Point O n l y , and apparently absorb the final traces of chlorine. In this manner, by a have not dissected the reaction. The same is true of the simple glance at the flowmeter readings exactly what was 1 Presented before the Division of Rubber Chemistry at the 65th OCCUrring at any particdar moment Of the reaction could be Meeting of the American Chemical Society, New Haven, Conn., April 2 to 7, 1923. 2 J. Chew. SOC.(London), 63, 686 (1888).
Y
4
J SOL.Chem. I n d , S9, 55 (1918). India Rubber J., 64, 981 (1922).
