April, 1929
INDUSTRIAL A N D ENGINEERING CHEMISTRY
35’7
Absorption of Oxygen by Alkaline Tannates’ E. P. Fager and A. H. Reynolds DEARBORN CHEMICAL COMPANY, CHICAGO,ILL.
A study has been made of the absorptive properties of been based upon pract’ical exHE use of alkaline tanp e r i e n c e , very little being various commercial alkaline tannates in order that a nates for the removal comparison might be made of their relative efficiencies known of the relative absorpof oxygen from boiler for use in boiler feed waters for the prevention of corrotive powers of the various waters, for the purpose of conextracts commercially availsion. For practical reasons, the investigation was trolling corrosion, has been able, and the conditions leadcarried out principally at room temperature and atpracticed for a number of ing to maximum efficiency. mospheric pressure with the assumption that the same years, although no definite inIt is to obtain some data on relative amounts of oxygen would be absorbed at higher formation is available as to these phases of the subject temperature and pressure. It is shown that the comthe specific absorptive properthat this work has been unmercial tannins, in alkaline solution, absorb large ties of such materials. The dertaken. amounts of oxygen, in some cases almost as much as use of alkaline p y r o g a l l a t e alkaline pyrogallol. Experiments at higher temperadates back to 1867, when it Experiments at Room Temtures and pressures are now under way. was used by Bunsen,2as sugDerature and Atmospheric Pressure gested by Liebig, for the determination of oxygen. In addition to the use of pyrogallic It was first decided to investigate the faculty for absorbing acid for this purpose, tannic and gallic acids, and also tannin oxygen possessed by tannin extracts which are commercially extracts, have been used for the quantitative determination available, but to carry out this entire investigation a t boiler of oxygen,3 but these latter materials were never used ex- temperature and pressure was not considered advisable betensively because of a slower rate of absorption. cause of mechanical difficulties involved and the number of However, these investigations demonstrated that all tannins determinations to be made. It was decided to perform the hare a remarkable affinity for oxygen, especially in the pres- experiments a t room temperature and atmospheric pressure ence of alkalies.? Pyrogallic acid, gallic acid, and tannic and to assume that the various extracts would absorb relaacid are very closely related compounds, as is shown by their tive amounts of oxygen a t the higher temperature and presstructural formulas.5 They all have the property of absure. sorbing oxygen when in alkaline solution. When heated to The apparatus consisted of a Woulfe bottle modified as boiling, an alkaline solution of tannic acid hydrolyzes6 giving shown in Figure 1, a portable Orsat gas-analysis apparatus, gallic acid. Gallic acid, when heated to 200’ C. in the presa 2-liter aspirator bottle, and the necessary rubber-tubing ence of water, tends to be converted to pyrogallic acid and carbon dioxide. Thwefore, as tannin extracts contain large connections. Samples of various commercial extracts were obtained in amounts of tannic and gallic acids and other related comthe grades stated and in addition samples of c. P. tannic acid pounds, it would be expected that the absorptive power of and pyrogallic acid were tested. Moisture determinations tannins should be comparable to that of pyrogallic acid. were made on each of these samples by drying for 12 hours in The removal of oxygen from boiler mater is, no doubt, one an oven maintained a t 220’ F. (104.4’ (3.). The results are of the prime considerations in the control of corrosion. Acgiven in Table I. cording to Buswell,’ Speller,S and others the removal of oxygen, when conditions are such that it can be accomplished, Table I-Moisture C o n t e n t of Various Tannin Extracts EXTRACT MOISTURE EXTRACT MOISTURE comes nearer to preventing corrosion completely than any Per cent Per cent other treatment. The amount of oxygen present in boiler quebracho 12.1 Liquid myrobalan 57.8 feed water is perhaps the controlling factor of corrosion. If Solid Liquid quebracho 66,6 Liquid cbestnut-oak 56.8 cutch 21,O Solid chestnut-oak 8.3 the depolarizing effect of oxygen can be eliminated, one more Solid Liquid hemlock 60.3 Liquid spruce 43.0 54.9 Tannic acid ( c . P . ) 8.7 step in corrosion preyention is accomplished. The most con- Solid gambier 66,2 Pyrogallic acid (c. P . ) 3.3 venient method for its elimination would, no doubt, be the Liquid sumac absorpbion of the oxygen in the boiler itself by the use of The exact volume of the modified Woulfe bottle was dealkaline tannates introduced into the boiler as internal treat- termined by measuring the amount of water required to fill ment. The advantages of this method become more ap- it up to the stopcocks and was found to be 842 cc. parent when it is remembered that external methods of oxygen To determine the amount of oxygen that a sample of extract removal, such as de-aeration and the oxidation of scrap metal, was capable of absorbing, from 2 t o 5 grams were accurately require more or less apparatus and involve considerable main- weighed into a 250-cc. volumetric flask and run up to the mark tenance cost. with freshly distilled water. After all the water-soluble exThe use of tannates for the prevention of boiler corrosion tract had been dissolved, the flask was vigorously shaken and is not new, such materials having accomplished marked re25 cc. of the solution pipetted out. This was put into the sults over a period of time. However, the application has Woulfe bottle through the center opening and 35 cc. of dis1 Received October 24, 1928 tilled water were added. Then, after making sure that the 2 Bunsen, “Gasometry,” p. 79 (1867). two stopcocks were closed, 10 cc. of a 20 per cent potassium Watt, “Dictionary of Chemistry,” Vol V, p. 660; Vol 11, p 760, hydroxide solution were added as quickly as possible and the Vol IV, p. 311 (1868). central stopper was rapidly put in place. All openings were Beilstein, “Handbuch der organischen Chemie,” Vol. 11, p 1926 5 Trimble, “The Tannins,” Vol. I, p. 96. sealed with a layer of paraffin wax. Thorpe, Chemical Dictionary, Vol IV, p 440; Vol V, p 386. content of the air was determined in the regular ’ Buswell, “Chemistry of Water and Sewage Treatment,” p 145, wayThebyoxygen means of the Orsat, using a pyrogallol solution which Chemical Catalog Co , 1928. contained 40 grams of pyrogallic acid dissolved in 200 cc. 8 Speller, “Corrosion-Causes and Prevention,” p. 400.
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INDUSTRIAL AND EN(XNEERING CHEMISTRY
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of 20 per cent potassium hydroxide. The amount of oxygen contained in the Woulfe bottle was calculated by multiplying its total volume, less the volume of the solutions added to it, by the percentage of oxygen found in the air. The bottle containing the alkaline tannin solution was vigorously shaken for 3 to 4 hours. This amount of time was allowed for the absorption because it was desired that the action be complete before any determination was made of the oxygen absorbed. A sample of the gas above the solution was then drawn into the Orsat in the same manner as gas is taken from a gas-sampling tube. The aspirator bottle, filled with water, was used as a water head to force the gas into the machine. All connecting tubes were carefully filled with water before the sample was taken. The manifold of the Orsat was also filled with water before the samples were taken and the volume of gas was corr e c t ed accordingly. The volume of the Orsat manifold was found to be 1.5 cc. The percentage of oxygen in the sample from the Woulfe bottle was determined. If, on a d d i t i o n a l shaking of the bottle for 1 to 2 hours, a second gas a n a l y s i s showed no change in the percentage of excess oxygen, it was c o n c l u d e d t h a t the alkaline tannin-extract solution had removed all the oxygen that it was capable of removing. The excess oxygen remaining after absorption was calculated by multiplying the volume of gas Figure Bottle Woulfe originally present by the determined percentage of excess oxygen and correcting for the change of pressure. This was done by basing the calculations on the percentage of inert gas (Nz) originally present. Excess
0 2
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tannin solution would be affected in the same way. Accordingly a number of runs were made, in the manner described above, in which the concentration of extract was kept practically the same but the alkali concentration was varied widely. The results are given in Figure 2. I n these tests the liquid chestnut-oak extract was used. Experiments a t Higher Temperature and Pressure An effort was made to determine how the amount of oxygen absorbed a t higher temperatures and pressures would agree with the figures obtained in the foregoing experiments. Some experiments were run in a steel bomb a t 267' F. (130.6' C.), a t which temperature a pressure of around 25 pounds per square inch (1.67 atmospheres) was developed. With the equipment available there was a slight unavoidable leakage from the bomb. However, allowing for this leakage, it seems certain that the absorption of oxygen a t high temperatures and pressures is greater than it is a t room temperature and atmospheric pressure. The work is to be conducted a t higher temperatures and pressures and these results will be reported in a later paper. Discussion of Results These experiments show that all the commercial tannins tested have a marked affinity for oxygen when in solutions of sufficient alkalinity. The amount of oxygen that may be absorbed by some of the tannins is almost as great as that absorbed by alkaline pyrogallol. The waste liquors recovered by the sulfite pulp process, which are commonly called sulfite celluloses, do not have nearly so great an oxygen-absorbing power as do tannins recovered by water extraction.
(original volume of gas X Yo St beiore absorption YoNz after absorption original volume of Nz
1-
The difference between this figure and the amount of oxygen originally present is equal to the oxygen absorbed by the alkaline tannin solution. These figures expressed as cubic centimeters of oxygen removed per gram of extract are given in Table 11. T a b l e 11-Oxygen Absorbed b y Various T a n n i n Extracts OXYGENREMOVED OXYGEN REMOVED PER GRAM PER GRAM As recd. Dry As recd. Dry EXTRACT basis basis EXTRACT basis basis Solid quebracho 167 188 Liquid myrobalan 60 142 60 142 163 183 175 166 108 108
Liquid chestnut-oak
Solid cutch
76 72 85 85
Liquid hemlock
53 54
134 136
Liquid spruce
Solid gambier
48 48 59 58
106
Tannicacid. c.
Liquid quebracho
Liquid sumac
106 175 172
Solid chestnut-oak
P.
Pyrogallic acid, c.
P.
89 89 135 137
206 206 147 149
26 25
46 44
208 217 255 245
228 238 264 254
EFFECT O F VARYING ALKALICONCENTRATION-It has been shown by B e r t h e l ~ t ,and ~ again by Drakely and Nico1,'O that the total absorption of oxygen by an alkaline pyrogallol solution may be greatly affected by the strength of the alkali solution present, especially when its concentration is low. It is apparent that the amount of oxygen absorbed by an alkaline .
s Berthelot, Comfit. rend., 116, 1066 (1898). Drakely and Nicol, J . SOC.Chem. I n d . , 44, 454 (1925).
10
Figure 2
The tannins, when in their natural acid condition or when this acidity is just neutralized, show no tendency to absorb oxygen. When the amount of alkali is raised above that necessary t o neutralize, the oxygen that the solution is capable of absorhing increases very rapidly a t first and then less rapidly, until finally large differences in the alkalinity of the solution do not change its oxygen-absorbing power. This is in accordance with Berthelot's results on alkaline pyrogallol. The procedure followed in these experiments is not claimed to be extremely accurate, since a very small amount of oxygen may be absorbed in the Woulfe bottle after the alkali is added, before it could be stoppered. No gas machine, of the type used, is accurate beyond 0.1 cc. In the tests described this would represent a possible error of 0.5 per cent of the oxygen determined. However, the figures are relative and good checks can be obtained. Also, the amount of oxygen which alkaline pyrogallol was found to absorb by this method
April, 1929
INDUSTRIAL AND ENGINEERING CHEMISTRY
checked very well with the figures obtained by von KovitcsZorkhczy, l1 who found that 1 gram-molecule of pyrogallol would absorb approximately 40 grams of oxygen, which is equivalent to saying that at 86" F. (30"C.)and 740 mm. pressure, which are the conditions under which the writers' determinations were made, 1 gram of alkaline pyrogallol would absorb 253 cc. of oxygen. 11
Von KovLcs-Zork6czy. Biochem. 2.. 162, 161 (1925).
359
Conclusion
The foregoing experiments justify the belief that commercial tannins, in alkaline solution, have the property of absorbing large amounts of oxygen, and show the relative absorptive power of extracts from various sources. The principal industrial application of this property is in the prevention of corrosion in steam boilers where the presence of oxygen is the chief corrosion accelerator.
The Toxic Property of Sulfur' Chemistry in Relation to Toxic Factors Robert C. Williams and H. C. Young OHIOAGRICULTURAL EXPERIMENT STATION,WOOSTER,OHIO
Ordinary pure commercial sulfur for fungicidal The object of the present HE toxicity of sulfur to purposes has associated with it sulfurous acid, sulfuric i n v e s t i g a t i o n has been t o fungi has been attribacid, and pentathionic acid (tetrathionic acid). study the toxicity of sulfur in uted to various facA study has been made of the chemical and fungiits ordinary commercial forms tors-name1 y, sulfur itself, 11,* cidal properties of the acids of sulfur that are either and of the products accomsulfur dioxide or s u l f u r o u s associated with sulfur or are quite commonly known, panying or thought to be asacid,l2 sulfuric acid,' hydroand it has been found that the most toxic to spores of sociated with it. The invesgen s u l f i d e , * t h i o s u l f u r i c tigation includes both chemiacid,lo a n d p e n t a t < h i o n i c S. cinerea are the polythionic acids. Sulfur freed from this type of acid is not toxic. cal and fungicidal relationacid.16J6 ships. Filtrates from sulfur which has been quite thoroughly Of these, hydrogen sulfide wet owe a large part of their acidity to sulfuric acid. is definitely out of the controChemical Relationships of A solution of sulfuric acid, however, which has a total versy. Its identification unAcids of Sulfur acidity equivalent to that of a sulfur filtrate is not der conditions ordinarily asIn studying the chemical sociated with sulfur has not toxic. and fungicidal relationships of been established. FurtherArtificially oxidized sulfurs are very effective in the s u l f u r , t h e investigation of control of V. inaequalis provided the oxidizing agent more, solutions of it, even colloidal sulfur was not conthough equivalent in concenis not so effective as to destroy the polythionic acids. tinued, but ordinary stable trations to those acids which Field tests confirm laboratory tests. commercial forms of rhombic are toxic, may actually stimuA theory for the failure of sulfur applications conlate the germination of spores s u l f u r were used. Resubtaining alkaline constituents to control as well as those of X.cinerea. limed flowers of sulfur and which are acid is offered. Sulfur dioxide, or sulfurous high grades of ground roll acid, has no marked toxicity as such. Any toxicity that its sulfur were especially investigated. I n a preliminary note Young and WilliamslG gave evidence solution possesses is due to its hydrogen-ion concentration. Moreover, the quantity of sulfur dioxide associated with ordi- that pentathionic acid is associated with sulfur. This work nary sulfur is too small to be considered as a toxic factor. has been extended and the results are presented here. Sulfuric acid owes its toxicity to its hydrogen-ion concenWhen resublimed flowers of sulfur or ground roll sulfur was tration. Sulfur itself possesses no toxic effect when freed triturated with water to effect wetting and then filtered, the from accompanying products. YoungI5 and Young and Wil- filtrate was clear and possessed a definite titratable acidity. liamsI6working with various sulfur preparations, showed defi- Qualitative tests showed only the following acids in solution: nitely that pentathionic acid is toxic and pointed out that it sulfurous, sulfuric, and pentathionic (tetrathionic). It was accounted for the toxicity of all forms of sulfur. Their work noteworthy that sulfide ion and trithionate ion were absent. dealt with the study of Oden sulfur sols, acids of sulfur, and The reagents used for the qualitative tests were: finely divided ordinary sulfur. Pentathionic acid is present (sos)--: Iodine titration in considerable quantity in sulfur sols of that type and also (S20s) --: Iodine titration, with (SOa) -- bound by formalresults from oxidation in the presence of air and moisture in dehyde (SaOe) --: Mercurous nitrate the case of particulate sulfur. Tisdale14also considered penS--:Lead acetate, copper sulfate tathionic acid a toxic factor of sulfur. (SjO6) --: Ammoniacal silver nitrate, potassium hydroxide Recent work by Roach and Glynnelo was interpreted by ( 5 0 4 ) --: Barium chloride them as pointing to thiosulfuric acid as a toxic factor. HowTable I-Analysis of Filtrates f r o m Sulfurs ever, since thiosulfuric acid is a very unstable acid and since (Concentrations are given with reference to normal H ion) the conditions of their experiments were such as to insure the POLY- PERCENT presence of polythionic acids, the toxicity which they measTHIONIC POLYSULFUR TESTED ~~~~& H2SO4 A C I D ~ ~ THIONIC ured was undoubtedly that of the polythionic acids. Further(Bv diff.) ACIDS more, the tables given by them show a notable toxicity of Resublimed flowers 0,00253 0.00224 0.00029 11.5 pentathionic acid itself when compared with other acids Resublimed flowers 0.00190 0,00164 0.00026 13.7 tested. Ground roll 0.00129 0.00121 o.o0Oos 0.2
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Received November 28, 1928. text refer to bibliography at end of article.
* Numbers in
Ground roll a
0.00335
Tetra- and pentathionic acids.
0.00312
0.00023
8.7
