US2606873A - Composition for removing scale deposits from ferrous metal surfaces - Google Patents

Description

1 2 l 4 8 EXAMINE{R.;

Patented Aug. 12, 1952 2 05 373 2.806.873 COMPOSITION FOR REMOVING SCALE DE- POSIIS FROM FEBROUS METAL SURFACES Paul H. Car-dwell, Louis B. Eilers, and Billy P.

Robinson, Tulsa, Okla., assignors to The Dow Chemical Company, Midland, Micln, a corpo- 1 ration of Delaware No Drawing. Application February 27, 1950, .{f

Serial No. 146,622 19 Claims. (Cl. 252-148) 2 l V The invention relates to compositions for reare in the range of 2 to 15 per cent, about 5 to 10 1 moving scale deposits from ferrous metal surper cent being generally useful. Inasmuch asthe faces. It more particularly concerns an improved higher the acid concentration the more corrosive composition comprising hydrochloric acid for use and difllcult the acid is to inhibit, it is generally in removing scale deposits from iron or steel 5 desirable to use the acid in as low a concentration surfaces. as will serve to attack and remove the scale in a One of the well-known uses of hydrochloric satisfactory length of time.

acid is in treating iron and steel surfaces for the In accordance with the invention, we add to the removal of scale deposits such as those comprishydrochloric acid solution, which contains a suiting the various iron oxides or other foreign mat- 10 able concentration of HCl. formaldehyde and toter which is more or less soluble in the acid. Ingether therewith both an organic nitrogen base asmuch as the acid also attacks and dissolves and a wetting agent, suitable amounts and illussome o1 the metal underlying the deposits to be trative examples of these agents being given be- 1 removed, a corrosion inhibitor is added to reduce low. a) 1 the rate of attack of the acid upon the metal As to the formaldehyde, the usual commercial while the scale is being removed. Among the form is an aqueous solution containing about 40 substances known to reduce the corrosion of the per cent by weight of formaldehyde (I-ICHO) and r metal by hydrochloric acid solutions are the orsuch solution may be used conveniently as the *ganic nitrogen bases when present therein in source of the formaldehyde. The amount toemcomparatively small concentrations, the more efploy may vary over a wide range. It is desirable 1 3 fective ones being the aromatic and heterocyclic to have in the acid solution at least 0.002 per '1, nitrogen bases. Some pi the aldehydes in comcent by weight of HCHO but concentrations over paratively small concentrations are also known about 2 per cent by weight do not appear to be *7) '5; to reduce to a marked extent the corrosiveness of more effective than lower concentrations. In Q hydrochloric acid solutions, formaldehyde being terms of per cent by volume of the 40 per cent probably the most eiiective. For some purp s commercial formaldehyde solution, these amounts 310f imp in e ling of high Pr are 0.005 to 5.0 per cent of the volume of the acid ste generators with hydrochl ri a d So solution. An amount of the 40 per cent formaldewhere even a small loss of metal is undesirable. hyde ti hi i b t 0,05 per t by these substances either 8.10118 01 together (10 not volume of the acid solution is generally suital fle produce all the reduction in corrosiveness of hy- As t th organic nitrogen ba th r m ti drochloric acid solution to be desired, particulard w n t t amines 15 e 1y at the elevated tempe s requir to proferred as the do not chemicgl yx ct withthe duce descaling in a reasonably short time. 1 afiiifiifgu of e organic We have now discov r that y p oyi in nitrogen base in the hydrochloric acid solution the hydrochloric acid solution the organic nitromay vary over 9, wide range as long as an effective -ba i t r l n h the formaldehyde amount is present. Effective amounts to use. in th Pr enc of 8- W tin a ent. which has whenin combination with the other agents aforelittle or no inhibiting action in itself, but is capasaid, are in t order 1 t 2 cent, preble of promoting the wetting of the ferrous metal 40 {erred mncentrauon m per t, surface by the acid solution. a r y these proportions being by weight. Illustrative creased corrosion inhibitin effect is obtain d examples of suitable organic nitrogen bases to which exceeds that obtainable with either the employ are shown in Table I m the column rganic nitrogen base or the l y bothheaded "Organic Nitrogen Base." The invention then consists in the improved scale various wetting ag'ents, such as the synthetic removing composition hereinafter fully described detergents, may be employed which are stable and particularly pointed out in the claimsand dispersible or soluble in hydrochloric acid In carrying out the invention aqueous hydro solution and capable of promoting the wetting chloric acid is used in a concentration suitable of the ferrous metal surface by the aqueous s1u for decompo in dissolvmgdisintegrating the tion. There may be used as wetting agents scale deposits to be removed from the ferrous various organic sulfonates and sulfates inc1ud metal surfaces to which the acid solution is apmg those of Saturated hydrocarbons higher plied. Complete solution of the scale in the acid an ham alcohols as wen a aromatics solution is not always necessary. Some scale ti p S i ve examples of which appear in Table II with deposits contain both acid-soluble and acid-inm eir corresponding trade names in the column soluble constituents and usually slough off when t attacked by the acid without completely disheaded we ting Agentonly Small a unt solving. A wide range of concentration of HCl the Wetting agent need be mpl yed. as for may be used in the solution such as f m about 1 example from about 0.02 to 0.1 per cent by weight, to 30 per cent by weight, although other concen- -05 per cent bein generally sufll i nt. although trations may be used. Preferred concentrations other amounts may be used. L4)

" 3 a; L 'iML- Table II P t Corrosion Rate lbs.lsq. itJdey 1 eroen Wetting Agent by volume Row 511.0% 2,4,3-05111031 601 013011115) No. Formal- W iglit dehyde w 1 ht w ht w 1 m e e g 01g e 1; Name Percent Percent Rate Percent Rate Percent Rate o. 05 o. 705 0. 705 0. 705 Sodium benzene suli'onate 0. 05 0. 0. 347 0.293 0. l 0. 382 Oronite 0.05 0 05 0.307 0.307 0.307 g 0. 05 0.10 g. 122 g. 0. 1 3: a ig naphtha 0: 05 0.10 0134s 01223 0.10 0333 853 0.05 0. 05 0.347 0. 347 0.347 0. 05 0.05 0.10 0.159 0. 095 0.10 0. 221 0.05 0.709 0.709 0.709 Long chain alcohol suliate 0. 05 0. 0. 349 0. 300 o. 10 0. 337 [Merpol B" 0. 05 0. 05 0. 341 0. 341 0. 341 3.3 0.05 0.10 3.1% 3. 0.10 g. 7

8 E 0. 05 0. 10 0. 321 0. 337 0. 10 0. 333 T .23 0. 05 0. 05 0. 357 0. 357 0. 357 0. 05 0. 05 0. 10 0. 114 0. 091 0. 10 0. 133 0. 05 0. 599 0. 090 0. 390 Suliated hydroxy stearic acid 0. 05 0. 10 0.320 0. 237 0. 10 0.313 "Nopco 2031 0. 05 0. 05 O. 288 0. 288 0. 288 g. 0. 05 0. 10 g. 152 0 g 0. 10 g. 132 21-. .7

"Smmmem 3.3g 0. 05 0.10 g. 11% 3 20. mmbutylphenyb 0. 05 0.375 0. 234 0. 350 27. Imam) lt 0. 05 0. 429 0.420 0. 429 2a---- Areskapm .05 0.142 0. 0 70 0.151 131: Sodium momma 111111161111 0:32 33% 3:32 3:533 31. L P EP 0.05 0. 302 0.302 0. 302 33 3-23 231 0. 71 siildllmuutemtmydmmphma' 0. 05 0. 332 0.310 0. 307 2? 33} 0. 05 0. 331 0.381 0.331 0. 05 0.118 0.100 0. 155 0. 05 0. 705 0. 705 0. 705 Sodium xylene sulfonate 0. 05 0. 316 0. 331 0. 356 Naxonate G" 0. 05 0. 379 0. 379 0. 379 3'3? 3%; 3533 3'53 3 3 s 33 a 2 31 "Aemsd 0: 05 0 110 01 092 01 127 0. 05 0. 711 0. 711 0.711 Sodium diamyl suliosuccinate 0. 05 0. 361 0.371 0. 395 Aerosol AY" 0. 05 0. 390 0. 390 0.390 .32 0.11 17 0. 033 .121 0. 2 0.7 2 2 Fugium dihexyl suliosuccin- Amml 01 05 01 101 01003 01 135 0.05 0.703 0. 703 0. 703 Sodium dioctyl suliosuccinate 0. 05 0. 315 0. 289 0. 385 "Aerosol OT" 0. 05 0. 337 0. 337 0. 337 0. 05 0. 113 0. 10 0. 100 0. 131 0. 05 0. 730 91.031111111833713?! 3:32 373 3150 Dulma1 WA 0. 05 0. 05 0. 347

8%? M5 0 713 8 2 0 713 i ff ggg igg gfig 3:02 0. 05 0:350 ""030 01004 IIIIIIIIII 0: 350 Petmwet 0. 05 0.10 0.121 3.25%) 0.10 0.102

1 1 m 12.5% HCl was used for each test unless the corrosion rate exceeded 0.393 ibs./sq.it./day where 2 liters was used.

In the aforementioned Tables I and II, illustrative examples of acid compositions inhibited according to the invention are given. The examples show the efiect on the corrosiveness or the hydrochloric acid solution or the conjoint use of an organic nitrogen base, formaldehyde, and a wetting agent in the acid solution in accordance with the invention, in comparison with the efiect on the corrosiveness oi the acid solution of each agent alone, and combinations of two of the agents without the third agent. In obtaining the corrosion rate data set forth in both tables, sand blasted mild steel test pieces 2.68 inches long, 1 inch wide, and 0.13 inch thick, and substantially all alike as to corrodability, were immersed in separate vessels containing a quantity of the acid solution for 6 hours and the weight loss determined by weighing each test piece before and after the immersion. The acid solution was maintained at 175 F. and contained 2.5 per cent of HCl by weight. The volume of the acid solution was either 1 or 2 liters, as indicated, the volume being such that not more than about 10 per cent of the acid content or the solution was spent in each test. The corrosion rates reported are based upon the loss in weight of the test piece, the area of the test piece (6.32 square inches) exposed to the acid solution, and the duration of the immersion of the test piece in the acid, this test procedure being conventional in the art.

Referring to Table I, test No. 1 employed 2 liters of the hydrochloric acid solution at F. on a mild steel test piece as described, the corrosion rate thereby obtained wa 0.739 lb. per square foot per day as shown for test 1 in the last column. As indicated in the Table I, test No. 2 was run in the same manner as No. 1 but with 0.05 per cent by volume or 40 per cent formaldehyde added to the acid as shown for test No.

2 in the th column; the resulting corrosion rate was 0.345 pound per square foot per day as shown for test No. 2 in the last column. Test No. 3 was run similarly but with 0.05 per cent by weight of a wetting agent (column 6) consisting of a saturated straight chain hydrocarbon sulfate having an average of 8 to carbon atoms in the chain, instead of formaldehyde; the resulting corrosion rate was 0.745 pound per square foot per day (last column). Test No. 4 was run similarly to the others but the acid contained 0.05 per cent by volume of formaldehyde (column 5) and 0.05 per cent by weight of the wetting agent (column 6) the resulting corrosion rate was 0.348 pound per square foot per day (last column). Test No. 5 was run similarly but the acid contained 0.2 per cent by weight of the organic nitrogen-base dimethyl aniline alone (column 3); the resulting corrosion rate was 0.483 pound per square foot per day (last column). Test No. 6 was run similarly using 1 liter of acid which contained 0.1 per cent by weight of dimethyl aniline (column 4), 0.05 per cent by volume of 40 per cent formaldehyde (column 5) but no wetting agent; the resulting corrosion rate was 0.277 pound per square inch. Test No. 7 was similar to test No. 6 but the acid volume was 2 liters and contained 0.2 per cent by weight of dimethyl aniline, no formaldehyde, and 0.05 weight per cent of wetting agent; the resulting corrosion rate was 0.467 pound per square foot per day. Test No. 8 was similar to test No. 7 except that the acid contained 0.1 weight per cent of the organic nitrogen base instead of 0.2; the resulting corrosion rate was 0.525 pound per square foot per day. Test No. -9 was run similarly to the others and employed 1 liter of acid and it contained all three agents, viz". 0.1 weight per cent of the organic nitrogen base, 0.05 volume per cent of 40 per cent formaldehyde, and 0.05 weight per cent of the wetting agent; the resulting corrosion rate was 0.268 pound per square foot per day. Thus, it will be seen by comparing the corrosion rate figuresin the last column of Table I that the acid alone, i. e. test No. 1, is most corrosive. The presence of wetting agent alone, i. e. test No. 3, in the acid has but little effect on the corrosion rate. The formaldehyde alone, i. e. test No. 2, in the acid markedly reduces its corrosiveness, although the presence of the wetting agent along with the aldehyde, 1. e. test No. 4, does not materially affect the inhibiting action of the formaldehyde alone as the corrosion rate of test No. 2 is substantially the same as that of test No. 4. The presence of the organic nitrogen base alone, i. e. test No. 5, in the acid, like formaldehyde, markedly reduces the corrosion rate, but the presence of wetting agent along with this organic nitrogen base, i. e. test Nos. 7 and 8, either lowers (test No. 7) or raises (test No. 8) the corrosion rate depending upon the concentration of the base in the acid. But when the wetting agent is present along with both the organic nitrogen base and the formaldehyde in accordance with the invention as in test No. 9, the corrosion rate is reduced below that obtainable with any one of the agents or combinations of them including the combination of the organic nitrogen base and the formaldehyde, 1. e. test No. 9, without the wetting agent.

The effect of other organic nitrogen bases alone, in the presence of formaldehyde, in the presence of a wetting agent, and in the presence of both formaldehyde and a. wetting agent, on the rate at which the acid corrodes mild steel is 8 shown in the remaining tests 10 to 104, inclusive, of Table I. In all of these tests, it will be seen that the combined use of the three agents produces a greater reduction in corrosiveness than can be had from any one alone or any combination of two of them without the third.

The marked cooperative effect of the aforesaid three agents, viz. formaldehyde, the organic nitrogen base and the wetting agent is further illustrated by the data of Table II in which the corrosion rate data was obtained in the same manner as that of Table I. In Table 11, the effect of various wetting agents alone, in combination with formaldehyde, and in combination with both formaldehyde and one of the organic nitrogen bases 2,4,6-collidin e, qui ldine and isoquingline on e corrosiveness o the acid, 1's shown. In comparing the corrosion rates of Table II, one may refer to Table I for the corrosiveness of the acid alone (test No. 1, 0.739 pound per square foot per day) and for the acid with the organic nitrogen base alone (test No. 65, 2,4,6-collidine 0.360 pound per square foot per day; test No. 80, quinaldine 0.340 pound per square foot per day; test No. 90, isoquinoline 0.370 pound per square foot per day). In each of the rate columns of Table II, it will be seen that the corrosion rate reduction produced by the organic nitrogen base and the formaldehyde used together is greatly enhanced by the effect of the wetting agent even though it alone actually may make the acid more corrosive in some cases (e. g. row 1, 13, 25, 53) while in others it has only a slight corrosion reducing effect by itself, if any.

From the foregoing tabulated examples of the invention, it is not to be inferred that the invention is to be limited thereto as the invention contemplates broadly the use of formaldehyde combined with a wetting agent and an aromatic or heterocyclic nitrogen base in various concentrations of hydrochloric acid, the wetting agent being dispersible in the aqueous acid solution and capable of promoting the wetting of ferrous metal by the solution. It will be apparent that any one of the wetting agents may be used with any one of the organic nitrogen bases in formulating the acid composition including the formaldehyde. Also some of the organic nitrogen bases, as well as certain wetting agents, are superior to others in the combination. The particular choice of the two of the three agents to employ in the acid solution mainly will depend upon the amount of inhibition required as well as the cost of the materials. It has been found that particularly effective combinations are those including as the wetting agent an alkyl aryl sulfonate, such as sodium monobutyl phenyl-phenol sulfonate, sodium monobutyl biphenyl monosulfonate, and sodium isopropyl naphthalene sulfonate. Effective results are also obtained with aliphatic sulfonates as, for example, diisobutyl sulfosuccinate and sodium diamyl sulfosuccinate. Especially effective bases in the combination include 2,4,6-0 llidin quinaldine, is no quinohnmmetmohn efggd roportionsmwfii'n' these combinations are: 0.05 to 2 per cent for the bases, 0.02 to 0.1 per cent for the wetting agent.

This application is a continuation-in-part of our copending application Serial No. 717,078, filed December 18, 1946, now abandoned.

We claim:

1. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 1 to 30 per cent of HCl, from about 0.05 to 2 per cent of an organic nitrogen base selected from the group consisting of the aromatic and heterocyclic nitrogen bases, from about 0.002 to 2 per cent of HCHO, and from about 0.02 to 0.1 per cent of a wetting agent dispersible in the solution, said wetting agent being a compound of the group consisting of sulfated and sulfonated organic compounds.

2. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 1 to 30 per cent of HCl, from about 0.05 to 2 per cent of 2,4,6-collidine from about 0.002 to 2 per cent of HCHO, and from about 0.02 to 0.1 per cent of a wetting agent dispersible in the solution, said wetting agent being a compound of the group consisting of sulfated and sulfonated organic compounds.

3. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 1 to 30 percent of H01, from about 0.05 to 2 per cent of quinaldine, from about 0.002 to 2 per cent of HCHO, and from about 0.02 to 0.1 per cent of a wetting agent dispersible in the solution, said wetting agent being a compound of the group consisting of sulfated and sulfonated organic compounds.

4. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 1 to 30 per cent of HCl, from about 0.05 to 2 per cent of isoquinoline, from about 0.002 to 2 per cent of HCHO, and from about 0.02 to 0.1 per cent of a wetting agent dispersible in the solution, said wetting agent being a compound of the group consisting of sulfated and sulfonated organic compounds.

5. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 1 to 30 per cent of HCl, from about 0.05 to 2 per cent of quinoline, from about 0.002 to 2 per cent of HCHO, and from about 0.02 to 0.1 per cent of a wetting agent dispersible in the solution, said wetting agent being a compound of the group consisting of sulfated and sulfonated organic compounds.

6. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 1 to 30 per cent of 1101, from about 0.05 to 2 per cent of 2,7-dimethyl quinoline, from about 0.002 to 2 per cent of HCHO, and-from about 0.02 to 0.1 per cent of a wetting agent dispersible in the solution, said wetting agent being a compound of the group consisting of sulfated and sulfonated organic compounds.

7. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 1 to 30 per cent of H01, from about 0.05 to 2 per cent of an organic nitrogen base selected from the group consisting of the aromatic and heterocyclic nitrogen bases, from about 0.002 to 2 per cent of HCHO, and from about 0.02 to 0.1 per cent of sodium monobutylphenyl-phenol monosulfonate.

8. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 1 to 30 per cent of 10 HCl, from about 0.05 to 2 per cent of an organic nitrogen base selected from the group consisting of the aromatic and heterocyclic nitrogen bases, from about 0.002 to 2 per cent of HCHO, and from about 0.02 to 0.1 per cent of sodium monobutyl biphenyl monosulfonate.

9. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 1 to 30 per cent of HCl, from about 0.05 to 2 per cent of an organic nitrogen base selected from the group consisting of the arcmatic and heterocyclic nitrogen bases, from about 0.002 to 2 per cent of HCHO, and from about 0.02 to 0.1 per cent of the sodium sulfate ester of 2-ethyl hexanol-l.

10. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 1 to 30 per cent of 1101, from about 0. a 2 r cen of an organic trond heterocy from about 0.002 from about 0.02 to 0.1 per cent of sodium diisobutyl sulfosuccinate.

11. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 1 to 30 per cent of HCl, from about 0.05 to 2 per cent of an organic nitrogen base selected from the group consisting of the aromatic and heterocyclic nitrogen bases, from about 0.002 to 2 per cent of HCHO, and from about 0.02 to 0.1 per cent of diamyl sodium sulfosuccinate.

12. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 2 to 15 per cent HCl, from about 0.05 to 2 per cent of 2,4,6-collidine, from about 0.002 to 2 per cent of HCHO, and from about 0.02 to 0.1 per cent of sodium monobutyl phenyl-phenol monosulfonate.

13. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 2 to 15 per cent of H01, from about 0.002 to 2 per cent of HCHO, from about 0.05 to 2 per cent of quinaldine, from about 0.02 to 0.1 per cent of sodium monobutyl phenyl-phenol monosulfonate.

14. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 2 to 15 per cent of HCl, from about 0.002 to 2 per cent of HCHO, from about 0.05 to 2 per cent of isoquinaline, from about 0.02 to 0.1 per cent of sodium monobutyl phenyl-phenol monosulfonate.

15. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 2 to' 15 per cent of HCl, from about 0.002 to 2 per cent of HCHO, from about 0.05 to 2 per cent of quinaldine, from about 0.02 to 0.1 per cent of sodium monobutyl biphenyl monosulfonate.

16. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 2 to 15 per cent of HCl, from about 0.002 to 2 per cent of HCHO, from about 0.05 to 2 per cent of isoquinoline, from 11 about 0.02 to 0.1 per cent of sodium monobutyl biphenyl monosulfonate.

17. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 2 to 15 per cent of HCl, from about 0.002 to 2 per cent of HCHO, from about 0.05 to 2 per cent of quinaldine, from about 0.02 to 0.1 per cent of the sodium sulfate ester of 2-ethyl hexanol-l.

18. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution of hydrochloric acid containing by weight from about 2 to 15 per cent of 1101, from about 0.002 to 2 per cent of HCHO, from about 0.05 to 2 per cent of quinaldine, from about 0.02 to 0.1 per cent of diisobutyl sodium sulfosuccinate.

19. A composition for removing scale deposits from ferrous metal surfaces comprising an aqueous solution oi hydrochloric acid containing by weight from about 2 to 15 per cent of HCl, from about 0.002 to 2 per cent of HCHO, from about 0.05 to 2 per cent of quinaldine, from about 0.02 to 0.1 per cent of diamyl sodium sulfosuccinate.

PAUL H. CARDWELL.

LOUIS H. EEERS.

BILLY P. ROBINSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,470,225 Holmes Oct. 9, 1923 1,678,775 Gravell July 31, 1928 2,070,487 Lutz Feb. 9, 1937 20 2,425,320 Hill Aug. 12, 1947

Claims (1)

1. A COMPOSITION FOR REMOVING SCALE DEPOSITS FROM FERROUS METAL SURFACES COMPRISING AN AQUEOUS SOLUTION OF HYDROCHLORIC ACID CONTAINING BY WEIGHT FROM ABOUT 1 TO 30 PER CENT OF HCL, FROM ABOUT 0.05 TO 2 PER CENT OF AN ORGANIC NITROGEN BASE SELECTED FROM THE GROUP CONSISTING OF THE AROMATIC AND HETEROCYCLIC NITROGEN BASES, FROM ABOUT 0.002 TO 2 PER CENT OF HCHO, AND FROM ABOUT 0.02 TO 0.1 PER CENT OF A WETTING AGENT DISPERSIBLE IN THE SOLUTION, SAID WETTING AGENT BEING A COMPOUND OF THE GROUP CONSISTING OF SULFATED AND SULFONATED ORGANIC COMPOUNDS.