36
INDUSTRIAL A N D ENGINEERING CHEMISTRY Literature Cited Cade, Chem. Met. Eng., 29, 319 (1923). Decker and Koch, Ber., 40, 4794 (1907). Dumas and Peligot, Csnlralblatl. 1836, 279. Fisher, "Laboratory Manual of Organic Chemistry," p. 180, Wiley,
1924. Graebe, Ber., 38, 152 (1905). Rlemenc, Monatsh., 38, 555 (1917). Kostanecki and Lampe, Ber., 37, 774 (1904); 41, 1330 (1908).
Vol. 22, No. 1
(8) Lewis, Mason, and Morgan, IND. ENG.CHEM.,16, 811 (1924). (9) Lewis and Trieschmann,Proc. Iowa. Acad. Sci., Si, 282 '(1924); C. A , , ao, 2319 (19.~6). (10) Liebig, Ber., 87, 4036 (1904). (11) Meyer. Ibid., S I , 4144 (1904); 40, 2432 (1907). (12) Perkin and Robinson, J . Chem. Soc., 91, 1079 (1907). (13) Ullmann and Wenner, Ber., SS, 2476 (1900). (14) Wegscheider, Monatsh., as, 383 (1902). (15) Werner and Seybold, Ber., 87, 3658 (1904).
Boiler Reactions at High Temperatures' Boiler Corrosion at 10.54 and 14.06 kg. per sq. cm. Pressure Wayne L. Denman2 and Edward Bartow UNIVERSITY OF
IOWA,IOWACITY, IOWA
Boiler corrosion has been studied under apgroxiE N E R A T I O N of watts. Water was added by mately actual operating conditions by means of a small steam within boilers means of an injector and the laboratory boiler. A modified form of apparatus for results in a concentraamount of water present in cleaning t h e test plates by reduction with hydrogen tion in the feed water of mathe boiler was determined liberated from t h e plates, as they served as t h e cathodes terial consisting of suspended with a platform scale on in an electrolytic cell, gave very good results. solids and s o l u b l e salts. which the boiler was placed. It has been found t h a t corrosion is directly proThis material, together with I n the corrosion tests, charportional t o t h e amount of dissolved oxygen; t h a t the several gases commonly coal-iron plates, 9.9 X 5.0 X caustic alkalinity, dichromates, and arsenites inhibit found dissolved in water, 0.25 cm., were suspended by corrosion when present in sufficient quantity; and causes boiler troubles which means of small wire as shown t h a t t h e removal of dissolved oxygen by means of remay include scale formation, in Figure 1. Three or 4 plates ducing agents such as red-oak extract or sulfur dioxide foaming and priming, embritwere used in each test. At results in greatly reduced corrosion. Removal of tlement, and corrosion. Of the end of the test the oxide dissolved oxygen is accomplished with t h e minimum these, corrosion is by far the layer must be removed. Probof corrosion by the use of oak extract. If an inhibitor most serious. ably the best method for this such as potassium dichromate is used in t h e presence Various theories, including is that of Jacob and Kaesof a high chloride concentration, extreme care m u s t the carbonic acid theory, the bohrer (4). They placed the be taken to insure t h e addition of sufficient inhibitor. peroxide theory, and the coltest plates in an electrolytic If too little is added, t h e resulting corrosion is highly loidal theory, have been used cell as cathodeswith platinum localized and more severe than when n o inhibitor is to explain the mechanism of or carbon anodes. The hydropresent. corrosion,but noneis so logical gen liberated on the cathode Determination of t h e concentration of boiler water as Whitney's electrolytic hydisintegrates a n d r e d u c e s may be accomplished by means of analysis of alkali pothesis (6). He showed that the oxide film to a finely metals or chlorides. The use of chloride is by far t h e iron, by virtue of its solution divided mass, which may most convenient. pressure, will displace hydrobe removed quantitatively gen from solution in water with a stiff brush. I n this with the formation of ferrous work a modification of their ions. Equilibrium is determined by the rate of diffusion of method was used. Sodium sulfate served as electrolyte. oxygen to the surface, the rate of reaction of the liberated I n the tables the extent of corrosion is tabulated in two hydrogen with oxygen, and the rate of formation of molecu- columns. The first column is merely the average loss in weight of the test plates in milligrams, while in the lar hydrogen. Considerable work on boiler corrosion has been published, second column the values are calculated from the following but little of it was done with laboratory equipment. Boss- formula of Bosshard and Pfenniger (1): hard and Pfenniger (1) investigated the behavior of iron in a number of salt solutions using a small laboratory boiler. in wt. (mg.)x 10 c = Area (sq.Loss They found that magnesium chloride was the most corrosive dm.) X (30 liters feed water) and that sodium hydroxide was the least. Examination will show that C merely expresses the loss in General Experimental Procedure milligrams per square decimeter per 10 liters of feed water. The pressure is maintained within narrow limits for a The writers have investigated corrosion problems under period of 24 hours. The initial rate of corrosion is the most conditions which approximate, as closely as possible, those rapid, and after the oxygen present is exhausted corrosion encountered in actual operation of steam boilers. To this practically ceases. Although the oxygen is used up in less end, a small boiler 12 inches (30 cm.) in diameter by 24 inches than 24 hours, pFessure is maintained for that time in order (60 cm.) long was constructed. (Figures 1 and 2) It oper- to insure equilibrium conditions and hence comparable results. ated a t a maximum pressure of 16.04 kg. per sq. cm. The I n this respect these tests, with the possible exception of electric heating unit gave three heats-1250, 2500, and 5000 those in which circulation takes place, are not directly com1 Received August 27, 1929. parable to conditions in an actual boiler, where the rate of 2 Abstract of thesis submitted by W. L. Denman in partial fulfilment reaction is of tremendous importance and final equilibrium is of the requirements for the degree of doctor of philosophy in the Graduate rarely approached. For example, a boiler fed with water College of the State University of Iowa, January 29, 1929.
G
+
INDUSTRIAL A N D ENGINEERIhTG CHEMISTRY
38
T a b l e 11-Action of R e d u c i n g Agents Used in Combating. Corrosion [At 14.06 kg. per sq. cm. (200 lbs. per sq. in.) pressuie] Av. DUCING LOSS I N APPEARANCE OF SAMPLES AGENT KOH SO1 C1 WT. C Before electrolysis After electrolysis
RE-
INITIAL DISVOL.
SOLVED
37.6 36.5 37.8 38.3 37.9
5.39 5.42 5.65 8.0 5.85
Vol. 22, s o . 1
RUN WATER OXYGEN PH Lzlers P . 0. m. P.0.m. P . 9 . m . P . 9 . m . P . 9 . m . Mg. PYROGALLIC ACID
1 2 3 4 5
0.0 0.0 9.5 17.6 35.2
60.6 15.0 74.0 74 0 74.0
13.9 18.4 11.7 12.5 10.3
3.48 4.74 2.88 3.07 2.57
Light brown Light brown Light brown Light brown Dark brown
Light Light Light Light Light
Thick layer of dark red rust Thick layer of dark red rust Thick layer of dark red rust Thick layer of dark red rust Verv thin laver of oxide VerG thin la$er of oxide Very thin layer brown oxide Thin layer oxide
Dull gray Dull gray Dull gray Bright gray Bright Prav Bright &a$ Bright gray Bright gray, few spots
Red oxide layer Brown and spotted Light brown, spotted Thin black layer Light brown, spotted Dark brown
Spotted gray Gray, spotted Gray, spotted Gray Gray, spotted Gray
gray gray gray gray gray
OAK EXTRACT
SULFUR DIOXIDE
1 la 2 2a 3 3a
RUN
36.9 35.0 37.4 36.2 36.9 37.3
0.0 33.6 0.0 30.1 0.0 28.1
7.2 8.2 6.3 6.3 6.1 6.8
INITIAL VOL. DISSOLVED WATER OXYGEN PH
Liters
P . 9. m.
124 86 126 78 127 80
289 289 289 289 797 779
39 39 141 149 39 39
46.8 21.3 117.2 76.2 147.5 102.3
11.9 5.7 29.5 19.9 37.6 25.8
T a b l e 111-Effect of I n h i b i t o r s in R e d u c i n g Corrosion sa. cm. (200 lbs. per sq. in.) pressure] [At 14.06 ka. - per . Av.
INHIBITOR P . 9 . m . P . 0. m.
LOSS I N
C
WT.
APPEARANCE O F SAMPLES
Before electrolysis
After electrolysis
ME.
ARSENIC COMPOUNDS
AszOa
NazHAsaOs
1 2 3 4 5 6
313 15.6 16.1 17.7 21.2 25.5
77.8 3.87 4.03 4.40 5.20 6.32
Dark brown Light brown Light brown Light brown Dark brown Dark brown
Gray Gray Gray Gray Gray Gray
6.2 40.4 232 162 217 f16.9 1-28.4
1.5 10.0 56.9 39.9 54.0 4-4.17 $6.60
Slight corrosion Local corrosion Local dark red corrosion Even black Severe local corrosion Certain areas highly colored Blue green and purple
Gray with blue areas Light blue to purple Light blue to purple Gray Blue to purple and pitted Same areas blue t o purple Brightly colored
POTASSIUM DICHROMATE
NaCl 1 2 3 4 5 6 7
38.3 37.7 38.2 38.1 37.8 37.5 37.6
5.23 5.04 5.33 5.95 4.90 5.53 5.67
5.6 5.8 5.8 6.9 5.7 5.5 5.3
14.5 14.3 14.3 14.2
KnCrzOr 47.6 24.0 4.8 0.0 47.8 95.8 189
Corrosion Tests with Inhibitors
Certain substances have the property of giving protection to metals, presumably by the formation of protective films. Tests were conducted with two substances of this typearsenic compounds and potassium dichromate. The experimental values are summarized in Table 111. ARSENICCo~~PouNDs-When a piece of iron is immersed in a solution containing arsenic, metallic arsenic is deposited on the iron owing to the relative position of the two metals in the electromotive series. Gunderson (3) claimed that the deposition of arsenic resembled amalgamation of a zinc electrode. Lloyd (6) added arsenic trioxide t o a slightly acid water flowing through iron pipes and found that corrosion was greatly reduced. Arsenic trioxide alone resulted in excessive corrosion, as there was no alkali present. Sodium arsenite, on the other hand, reduced the corrosion in every case. The amount of corrosion is inversely proportional to the concentration of sodium arsenite. Also, variations in the dissolved oxygen content do not seem to have much influence on the extent of corrosion. POTASSIUM DIcHRomTE-Chromates have been used in boiler protection and are said to cause a passive condition by the formation of a protective film. Experience has shown that this condition is difficult to obtain in the presence of halogens. When potassium chromate is present as an inhibitor, corrosion is greatly reduced, but as the concentration of the inhibitor is diminished, the amount of corrosion increases enormously. This increase is undoubtedly due to the fact that when protective films are formed greatly accelerated corrosion will ensue if the film is not made strong enough.
Sodium chloride alone causes greatly accelerated corrosion. When potassium dichromate (47.8 p. p. m.) was added, severe local corrosion took place. This indicates that salt solutions break down protective films, causing severe local action. Raising the chromate treatment resulted in an unusual phenomenon. Instead of reducing the amount of corrosion to a small value, the test plates actually gained in weight. The surfaces were highly colored and only slight local action was evident. Examination of the metal surface showed that chromium was present. T a b l e IV-Corrosion w i t h C i r c u l a t i o n of Feed W a t e r [ A t 10.54 kg. per sq. cm. (150 Ibs. per sq. in.) pressure] 1x1To- Av. TIAL GAL LOSS APPEARANCE OF SAMPLES VOL. VOL. I N Before After RUN WATERWATERWT. C electrolysis electrolysis
Mg.
Liters
Liters
1 2
37.2 28.0
145.2 26.2 1.69 1 2 6 . 1 1 5 1 . 3 11.29
3 4 5
31.2 34.2 37.4
163.9 104.0 5 . 9 9 183.5 87.1 4.46 161.9 7 1 . 7 4 . 1 7
6 7 8
37.6 38,5 37.0
158.1 46.2 2.69 144.5 58.4 3.53 145.2 58.2 3.77
Bright red layer of rust Compact red coating of rust Compact layer of rust Compact layer of rust Compact and thin layer of rust Thin layer of brown rust Thin layer of brown rust Dark red layer of rust
Gray Gray Bright gray Bright gray Bright gray Brightgray Bright gray Bright gray
Corrosion Tests with Circulation of Feed Water
These tests were carried out by allowing a certain amount of steam to escape into the condenser and making up the loss by fresh feed water. Except for the first run, softened water was used. The results are summarized in Tables IV and V. A lower pressure, 10.54 kg. per sq. em. (150 lbs. per sq. in.), was used in order t o allow more rapid circulation of feed water. Lime-soda-softened water was used in runs 2,
January, 1930
IA’DCSTRIAL AKD ENGINEERING CHEMISTRY
3, 4, and 5, while zeolite-softened water was used in runs 6, 7 , and 8. This feed water averaged about 7 p. p. m. dissolved
oxygen.
1. 2.
Table V-Determination of Concentration“ of Feed Water [At 10.54 kg. per sq. cm. (150 lbs. per sq. in.) pressure] ALKATOTAL SO& LINITY NaCl WATER SOLIDS C1 P.p.m. P.p.m. P.p.m. P.p.m. P . p . m . P , p . m . Feed water 145.2 Concentrate Distilled water 17.1 Concentration 8,5 Feed water 30.0 275.0 115.0 382.6 126.0 569.0 Concentrate 245.0 2232.0 140.0 3137.0 15.2 4115.0 Concentration 8.16 8.12 ... , 8.19 8.3 7.2 Feed water 29.0 275.0 110.0 382.3 163.9 607.0 Concentrate 262.4 2474.0 180.0 3461.0 1 8 . 3 4437.0 Concentration 9,05 9.0 , ,. , 9.06 9.0 7.3 Feed water 29.6 274,8 86,5 400.3 183.5 571.0 Concentrate 360.0 3359.0 274.0 4884.0 15.1 6132.0 Concentration 12.16 12.23 .,, ,. 12.2 12.2 10.7 Feed water 29.3 276.0 69.0 4 0 1 , 3 161.9 554.0 Concentrate 385.0 3616.0 350.0 5237.0 1 2 . 4 6654.0 Concentration 13.1 13.1 .,, ., 13.0 13.0 12.0 732.5 1581 784.0 287.0 Feed water 38.0 286.0 1 7 . 2 6716.0 2582.0 2543.0 6450.0 Concentrate 346.0 9.0 9.2 8.6 Concentration 9.1 8.9 S.95 144.5 1035.0 336.0 285.0 Feed water 147.0 984.6 17.2 8274.0 Concentrate 1 2 4 0 . 0 2 8 4 8 . 0 2 3 2 3 . 0 8287.0 8.49 8.16 8.4 8.0 Concentration 8.45 8.42 145.2 1331.0 Feed water 371.0 293.0 285.0 1326.0 Concentrate 3180.0 2549.0 2406.0 11256.0 1 7 . 0 10860.0 Concentration 8.58 8.56 8.45 8.50 8.5 8.1 a Coccentration equals ratio concentrate to feed water.
.
3.
.
4. 5. 6.
7. 8.
Distilled water gave the least corrosion. The amount of residual alkalinity in runs 2, 3, 4, and 5 increased and the
39
corresponding values of corrosion decreased accordingly. Zeolite-softened water always gave less corrosion than the lime-soda-softened water. This is probably due t o the higher alkalinity. Concentration of Feed Water
Various methods have been used in determining the coilcentration of boiler water. The determination of the ratio of chloride in the feed water to that in the boiler water seems to be in the best favor. A partial analysis of the feed mater and boiler water is given in Table V for the purpose of calculation of the concentrations. Neither the alkalinity nor the total solids could be considered with the lime-soda-softened water. However, the ratios of the values of chlorides, sulfate, sodium chloride, and water agree quite well. The values for sulfate could not be used on account of deposition of calcium sulfate within the boiler. Good agreement is obtained between all the values, with exception of total solids, in the case of the zeolite-softened water. This discrepancy is caused by the hydrolysis of sodium carbonate t o sodium hydroxide. Literature Cited Bosshard and Pfenniger, Chem - Z l g , 40, 5, 46, 63, 91 (1916) Fager and Reynolds, IND ENG CHEM, 21,357 (1929). Gunderson, Razlway R e s , 79, 335 (1926). Jacob and Kaesbohrer, Chem - Z t g , 35, 877 (1911). Lloyd, Trans A m lnst Mzn E n s , 39, 814 (1908) ( 6 ) Whitney, J. A m Chem Soc , 25, 394 (1903) (1) (2) (3) (4) (5)
DAIRY CHEMISTRY SYMPOSIUM Papers presented before the Division of Agricultural and Food Chemistry at the 78th Annual Meeting of the American Chemical Society, Minneapolis, Minn., September 9 to 13, 1929
Some Recent Advances in the Chemistry of Milk’ L. S. Palmer DIVISIONO F AGRICULTURAL BIOCHEMISTRY, UNIVERSITY
M
ILK and its various products continue to be of interest to chemists all over the world. During 1928 Chemical Abstracts covered 336 articles under the general headings of hlilk, Milk Analysis, Butter, Cheese, Ice Cream, Cream, and Buttermilk. These are exclusive of books and patents. Although I have arbitrarily selected the work reported in 1928 and 1929, it is obviously necessary to limit myself to just a few of the recent papers. For convenience, I have grouped the papers to be mentioned under several topical headings. Milk Analysis The determination of the fat content of milk and its products would appear to be so well established that no new problems would arise in connection Kith it. However, Thurston and Peterson (15) have shown that very large errors may be involved in applying to buttermilk any of the well-known gravimetric methods for fat, because buttermilk has a relatively high concentration of compound and derived lipides of the lecithin and sterol types, especially the former. Agricultural chemists, of course, have recognized for years that the ether extract of many plant and animal products is not true fat, but dairymen seemingly have assumed that the gravimet1 Received October 9, 1929. Published with the approval of the Director, as Paper No. 890, Journal Series, Minnesota Agricultural Experiment Station.
OF
MINNESOTA, ST. PAUL, MINN
ric procedures have given the true fat content of their products. Apparently dairymen will have to decide whether true fat or “ether extract” is what is desired and apply only such methods as give the correct value for the particular dairy product under examination. The Babcock test, which has long been held to be a practical rather than a strictly accurate method, apparently, under proper conditions will show the true fat content with greater accuracy than the more highly esteemed gravimetric methods. The problems presented here find special application in the estimation of fat losses in churning, as buttermilk seems to be especially rich in ether-extract substances that are not true fat. Factors Influencing the Composition of Milk
Variations that may be produced experimentally or that occur naturally in the composition of cow’s milk continue to attract workers both here and abroad. New light is being thrown on some very old problems. For instance, Davies and Provan ( 2 ) show that the changes which are supposed to occur almost invariably when cows go to pasture depend to a considerable extent on the system of winter feeding and are especially pronounced when the winter diet has been low in protein. The increased concentrations of casein, total and inorganic phosphorus, and total calcium following the change from low-protein winter feeding to pasture, were
