I N D U S T R I A L A N D ENGINEERING CHEMISTRY
December, 1931
Literature Cited (1) Cryder and Frolich, IND.ENG.CHBM.,21, 867 (1929). (2) Fenske, Doctor’s Thesis, Mass, lnst. Tech., 1927. (3) Frolich, J . Soc. Chem. Eng., 47, 173 (1928). (4) Frolich, Davidson, and Fenske, IND. ENG. CHBX?.,21, 109 (1929). (5) Frolich, Fenske, and Quiggle, Ibid., 20, 694 (1928).
1389
(6) International Critical Tables, Vol. I, p. 350, McGraw-Hill, 1926. (7) Palmer, Proc. R o y . SOC.(London), 98, 13 (1920); 99,412 (1921); 101, 175 (1922); 103, 444 (1923); 106, 250 (1924); 107, 255 (1925). (8) Pease, J . A m . Chem. Soc., 45, 2296 (1923). (9) Smith, J . Chem. Soc., 123, 2088 (1923). (10) Smith and Wright, Ibid., 119, 1683 (1921). (11) Taylor and Burns, J . A m . Chem. Soc.. 43, 1273 (1921).
T h e Value of Silicate of Soda as a Detergent-11’ John D. Carter PHILADELPHIA QUARTZ CO., PHILADELPHIA, PA.
Dilute solutions of sodium silicates greatly decrease the deposition on cloth of various pigments from water suspensions. Soap also has marked power to protect the cloth. Mixtures of soap and silicate are a s good or better t h a n either alone with siliceous pigments. Other alkaline builders, with the exception of trisodium phosphate, show only slight power, or none a t all, to protect against deposition of pigments. Trisodium phosphate is intermediate between sodium silicate and the other builders in its power to protect the cloth. Starch in combination with alkaline materials gives some protection. Hide glue sols and alkaline sols of gum arabic and colloidal clay prevent deposition to a slight extent. Sodium silicates of all ratios decrease the deposition
of pigments on cloth. Especially a t great dilutions, t h e silicates of highest silica ratio have the most effect. Protective action depends on the amount of silica in solution a s silicate, rather t h a n on the sodium oxide content. Deflocculation is inadequate as a n explanation. Solid dirt may be removed from one piece of cloth and deposited on another piece or section by the same detergent solution. Sodium silicate (Na20:3.25Si02) has marked powers in both the removal and the protection. The action of the silicate is primarily on the cloth rather t h a n on the pigment, although there is some effect on the latter. Presumably the protective action is due t o a n extremely thin film formed on the cloth. This film is easily removed by rinsing, and therefore no residue is left. This makes it difficult to determine itecomposition.
.. .. * . .. IKE many other everyday processes, that of washing
tinued for 5 hours, and the dirt was beaten into the soiled fabrics has been shown in recent years to be very cloth so that it could not he removed on subsequent washing. complicated fundamentally. Stericker ( 6 ) , in the first Under these conditions the lather would probably have been article of this series, listed the following factors as having a destroyed, and there was no indication by the authors that part in detergent processes: “Emulsification, wetting, lubrica- redeposition was a frequent occurrence. Spring ( 5 ) showed tion, deflocculation, solution, foaming, and perhaps others that soap prevented the deposition of purified lampblack on which have been overlooked or which are not yet known.” filter paper, and Chapin (2) found that soap, particularly acid In much of the work of the past it has been assumed that the soap, “inhibited the adsorption of suspended carbon black by whole duty of a detergent solution was to remove dirt with the fabric.” The latter stated that this was not a measure of the least possible injury to the fabric. An extended series of detergency, and neither of them seems to have observed retests by the writer (only part of which are reported in this deposition or recognized it as a factor in detergency. article) indicates that this assumption is not justified, and Many other experimenters have made the assumption that that another factor, which might be called “protection against any liquid which is efficient in removing dirt from a fabric will deposition, or redeposition,” should be added to the above list. likewise be capable of protecting that fabric, or similar fabric When a piece of cloth, soiled either with pigment alone or with in the same liquid, from any soiling action of the material soiling mixtures containing starch or oil, was washed together which has been removed. Therefore, it appeared that this with a clean white piece, it was found that the clean piece concomitant removal and deposition was worthy of further took up more or less color which had been removed from the study. I n this paper the conditions under which the deposisoiled piece. Under some conditions this redeposited pig- tion of pigments, taken as representative of solid dirt, takes ment was removed again as both pieces were repeatedly place will be discussed first, followed by the more complicated washed together. I n other cases the pigment remained at- phenomenon of redeposition. All the experiments described tached with great tenacity to the piece which was originally here were carried out with distilled water. The effect of clean, even though it was almost completely removed from the various constituents occurring in hard and softened waters piece which was originally soiled. Such a condition is ob- will be described in a later article. viously too important to be neglected in consideration of Apparatus washing processes. Furthermore, it is evident that it is the part of wisdom to prevent redeposition rather than to try t o LAUNDEROMETER-MOSt of the tests described below were remedy it after it has taken place. performed in a launderometer* (1). It has been recognized that lather holds the insoluble-dirt This (see Figure 1) consists of a metal tank with rounded and prevents its redeposition. I n the absence of lather it has bottom, supported in an open metal framework. Through the been believed (3) that insoluble soiling agents “are removed middle of the tank there passes a shaft supported on bearings. from one support and deposited on another.” Rhodes and This shaft carries four rows of threaded posts, equipped with Brainerd reported (4) two experiments in which redeposition 3 This machine has been adopted as a standard by the Detergents occurred upon prolonged washing. The agitation was con- Committee of the American Oil Chemists Society and by the American
L
1
Received October 22, 1930.
Association of Textile Chemists. Company, Chicago, Ill.
I t is made by the Atlas Electric Devices
1390
INDUSTRIAL A N D ENGTINEERING CHEMISTEY
the tank is a perforated pip; gas burner. This is used t i h i a t water with which the tank is filled to the levcl of the shaIt, and thercby maintains a constant temperature. The mechanical action produced by t h c rotation of the shaft is augmented hv placing a number of small rubber or metal balls in each jar.
Vol. 23 No. 12
was suspended. The cloth from the first Came out a deep red, while that from the second was a pale pink. When the shaking was continued for 30 minutes at a temperature of 60' C., the difference between the two pieces of d o t h was even more pronounced, as is shown in Figure 3. It is evident that the silicate prevented, to a large extent. the deposition of the ferric oxide.
OTHERSoiLs--Of course, ferric oxide is not a rommon constituent of dirt as i t ordinarily occurs in soiled fabrics, and was chosen in the above experiment only because of its bright color. However, a number of other experiments were run with different materials more or less related to actual soil or dirt, which showed that the action was general and not specific for any one pigment or class of pigments. A given amount of pigment was suspended in each of the following solutions: (A) Distilled water. (B) A solution of NaZ0:3.25SiOzwhich contained 0.197 per cent
total solids and 0.046 per cent Na20. (C) A solution. of sodium oleate which contained 0.2 per cent total solids. ( D ) A mixture of 4 volumes of (B) and 1 of (C) (E) A mixture of 1 volume of (B) and 2 of (C).
Figure l..--launderometer. Sldo View
PIIoToME.rER-The photometric measurements were made with aTaylor photometer as modified by tlhodes and Brainerd (4). With this instrument a difference in anDearance hetween two samples, giving readings which diffir.by 2, is very evident to the eye. The higher the reading. the whiter is the cloth.
These suspensions were then shaken with pieces of clean cloth for 1 hour at 60" C . The samples were then rinsed, dried, and compared. Tho soiling materials, their wncentrations, and the results are given in Table 1. Figures 4,5, and 6 show photographically the comparison between the silicate and water samples. ALKALINE h%ATEnIALS--TestS were run in order to determine the eficiency of other alkaline materials (often used as soap builders) in preventing the depositkin of finely divided pigments on cloth, either alone or with soap. A series of testa was conducted witli six pigments. carbon black, raw umber
Deposition
FERRIC OXIDE-A pair of simple experiments was made, which illustrates what is meant by the prevention of deposition. These may be easily repeated by anyone who is sufficiently interested. One gram of ferric oxide pigment and 100 ml. of distilled water were ptsced in a pint fruit jar. A piece of unsized Utica sheeting (any other clean cotton cloth containing little or no sizina may be used), 75 mm. square, was wet with water and placed in the suspension of pigment. The jar was closed and shaken for 2 minutes. The cloth was then removed and rinsed free
Puure +Ferric Olide Deposited on Oltron Cloth from Svspeneions in Water and In Dilute Na~0:3.25SIOI Solwfien (Time of eontab, 1 hour at 00'
C)
burnt umber, yellow ocher, vermilion, and ferric oxide. Stock suspensions in distilled water were made and diluted to the given concentrations with either water or detergent solution. Pieces of~clothwere then rotated in these suspensions for 1 hour a t 60" C . and rinsed free of loosely held pigment. The experiments were similar to those described above with sodium silicate, except that the silicate was replaced with some other alkaline material in each case. The results are given in Tables 11, 111, IV, and V, and the solutions used in place of (R), Table I, were made by dissolving each of the following in 2 liters of water:
.
..
prr cent N&O) to"represent modified soda. " Table V. 5.07 grams Nasl'0,:12H10 (0.066 per cent N%O
equivalent t o 0.044 per cent available NarO). from loosely held pigment by shaking with successive portions of rmter until these showed no color. The second test was exactly the same as the first, except that 0 5 gram of a 38 per cent solution (m. er. 1.394 = 41* Be.) of silicate of sods (Naao3.25SiOnj k a c added t o the water ih which the pigment
I n this series of tests there were some unavoidable variations in the pigments themselves and in the suspensions made from them. An idea of the variations can be obtained by comparing the water and soap figures in the different series. These gave clear indications that certain alkaline mate&
December, 1931
INDUSTRIAL A N D ENGINEERING CHEMISTRY
are much more effective tliaii others in preventing deposition or in aiding soap in this action. To remove any possible uncertainty, another series was made in which the principles were the same while the actual conditions were considerably altered. Vermilion was omitted, but the other five pigments were the same as were used in the earlier tests. Unsized Utica sheeting was cut into pieces 3 x 5 inches (7.6 x 12.7 cm.) and made into bags, each containing fifty 0.25-inch (0.635-em.) Monelmetal balls, similar to those used by Rhodes and Brainerd (4). One bag was placed in a launderoineter jar with 100 ml. of detergent solution and 1 gram of pigment. (Only 0.25 gram of carbon black was used.) The detergent solutions were the same as in the earlier tests, and the jars were rotated for 30 minutes at 60" C. The bags were thoroughly rinsed to remove the excess pigment, cut open, and dried on a smooth surface. The average photometer readings are given in Table VI. While in a very few cases the readings in different series of tests shoived a maximum variation as great as 5.5 in the percentage of whiteness, the mean deviation from the averages was only 1.7. Since different lots of pigments were used a t different times, it appears that the figures given are reproducible. I n any given series the agreement was closer. Since the figures given represent averages of 4 to 16 individual readings, averages which differ by 3.5, or more, certainly may be considered t o show differences in the detergent solutions. RESULTS WITH ALKALIKEMATERIALS-In the first Series Of tests Saz0:3.25SiO2alone reduced the deposition of all the pigments tried, except ground bituminous coal. With this pigment the water and the silicate solution gave exactly the same results, although the latter prevented the deposition of other forms of carbon. I n the later tests, probably because of the much higher concentration of exceedingly small particles in the carbon black, this silicate alone gave no protection. In general, silicate was less effective against large amounts of carbonaceous soils. With all the other soils and pigments it gave marked protection. Trisodium phosphate was less effective than the silicate but was better than any other alkaline material tried with all of the pigments except carbon black and vermilion. With these two pigments results were not as good as with water alone. Caustic soda, soda ash, and modified soda alone gave no protection except with raw umber. With this pigment a small amount of silicate may have been formed. RESULTSWITH SOAP-AS would be expected, soap solutions possess this power of preventing the deposition of pigments on cloth to a marked degree. However, in the case of soap this action may be interfered with by the presence of other materials, even though the ability to remove dirt remains largely unimpaired. This will be discussed more fully in a later article. A confirming series of experiments was also run, using mixtures of soap with various alkaline materials. The bag method previously described was used, and solutions of the builders prepared as before were mixed with a 0.2 per cent solution of sodium oleate in various proportions. The results are shown in Figures 7 to 10, inclusive. Again the marked superiority of silicate in preventing the deposition of pigments is clearly shown with everything except carbon black. In this case, probably because of the high concentration of exceedingly fine particles of pigment, there are no marked differences between the builders. Increased concentrations of pigment decrease the sensitivity of the test. Likewise, as the proportion of builder to soap decreases, the effect of the soap becomes greater, so that the differences between the different alkaline materials are less.
1391
T a b l e I-Effect of S o a p a n d S o d i u m Silicate S o l u t i o n s on Deposition of Soils a n d P i g m e n t s WHITEXESS, COMPARED WITH ORIGINAL COKCN. CLOTHWITH: PER Distilled Silicate So'ap Silicated Silicated SOIL OR PIGMENT LITER water (A) (Bj" (Cja soap (D)" soap(E)"
Grams Dust from Philadelphia building 0.10 Ground mica 0.50 Carbon black 0.05 Graphite 0.60 Ground b i t u m i nous coal 1.20 Ground wood 0.60 charcoal Ground animal 0.60 charcoal 0.50 Yellow ocher Raw umber 0:50 Burnt umber 0.50 Vermilion 0.30 Ferric oxide 0.30 Ultramarine Average 0 See text for descriptions
..
%
%
%
%
%
90.1
92.1 96.7 89.5 90.8
94.7 98.7 94.1 94.7
95.4 96.7 90.8 94.7
96.7 100.0 95.4 96.0
88.1 85.5
87.5
80.3
80.3
96.7
89.5
96.7
85.5
89.6
93.4
91.4
96.0
84.1 90.8 89.5 77.0 86.8 88.1 77.6 85.5 of these
90.1 96.0 93.4 88.1 94.7 95.4 92.8 91.5
96.0 94.7 98.0 89.5 95.4 94.7 91.4 94.8
90.8 98.7 98.0 90.1 100.0 96.0 92.1 94.2
94.7 97.4 97.4 92.1
E:$
92.1 95.8
solutions.
I
of S o a p a n d S o d i u m Hydroxide on Deposition of P i g m e n t s WHITENESS,COMPARED WITH ORIGINAL CONCN. CLOTH,WITH: PER Distilled Caustic Soap Built Built LITER water(A) soda (B) (C) soap (D) soap (E) Gram % % % % %
T a b l e 11-Effect
PIGMENT
0.50 0.25 0.25 0.25 0.60 0.30
Carbonblack Yellowocher Raw umber Burntumber Vermilion Ferric oxide Average
..
T a b l e 111-Effect
89.5 94.1 73.0 77.6 88.8 83.6 84.4
86.8 94.7 74.3 76.3 88.2 82.9 83.9
94.1 98.0 91.4 93.4 98.7 99.3 95.8
94.7 96.1 82.9 88.2 96.7 96.1 92.5
95.4 97.4 94.7 91.4 98.7 98.7 96.1
of S o a p and S o d i u m C a r b o n a t e S o l u t i o n s
on Deposition of P i g m e n t s
WITH ORIGINAL WHITENESS,COMPARED CLOTH,WITH: Sodium PER Distilled carbonate Soap Built Built LITER water (A) (B) (C) soap (D) soap(E) Gram % % % % %
COfrCN. PIGMENT Carbonblack Yellowocher Raw umber Burntumber Vermilion Ferric oxide Average
0.50 0.25 0.25 0.25 0.50 0.30
..
88.2 94.1 80.9 76.3 84.9 82.9 84.6
87.2 94.1 87.5 75.0 86.8 78.9 84.9
94.7 96.7 95.4 92.1 93.4 96.7 94.8
89.5 97.4 94.7 86.8 93.4 94.7 92.8
91.4 97.4 98.0 90.8 95.4 96.1 94.9
of S o a p a n d ModiEed Soda S o l u t i o n s on Deposition of P i g m e n t s WHITENESS,COMPARED WITH ORIGINAL CONCN. CLOTH,WITH: PER Distilled Modified Soap Built Built LITER water (A) soda (B) (C) soap (D) soap (E) Gram % % % % %
T a b l e IV-Effect
PIGMENT Carbon black Yellow ocher Raw umber Burnt umber Vermilion Ferric oxide Average
0.50 0.25 0.25 0.25 0.50 0.30
..
Carbonblack Yellowocher Rawumber Burnt umber Vermilion Ferric oxide Average
92.8 96.7 77.6 75.0 90.8 74.3 84.5
96.1 98.7 92.8 88.8 97.4 94.7 94.8
95.4 97.4 84.1 85.5 96.7 95.4 92.4
95: 4 98.7 92.8 87.5 97.4 97.4 94.9
of S o a p and Trisodium P h o s p h a t e S o l u t i o n s on Deposition of P i g m e n t s
T a b l e V-Effect
PIGMENT
91.4 96.1 74.3 75.7 88.2 77.0 83.8
WHITENESS,COMPARED WITH ORIGINAL CLOTH,WITH: CONCN. Trisodium PER Distilled phosphate soap Built Built LITER water (A) (B) (C) soap (D) soaD (E) Gram % % % % % . 0.50 88.1 86.8 96.1 89.5 90.8 0.25 0.25 0.25 0.50 0.30
..
93.4 78.3 75.7 89.5 79.6 84.1
94.7 84.1 80.9
86.8
78.9 85.4
96.7 91.4 89.5 98.0 95.4 94.5
96.1 84.1 87.2 96.7 93.4 91.2
98.0 87.2 87.2 98.7 95.4 92.9
of Soap Builders o n Deposition of P i g m e n t s o n C o t t o n C l o t h a t 60° C. (Percentage of whiteness compared with original cloth) MANFERRIC BURNT R A W YELLOW GANESE CARBON SOLUTION OXIDE UMBER UMBER OCHER DIOXIDE BLACK Water 5 0 . 5 ( 1 6 ) " 5 5 . 3 ( 4 ) 5 2 . 1 ( 4 ) 8 4 . 6 ( 4 ) 4 3 . 8 ( 4 ) 51 Q(10) NaOH 5 1 . 0 ( 8 ) 5 5 . 0 ( 6 ) 5 6 . 2 ( 6 ) 8 5 . 2 ( 6 ) 4 5 . 9 ( 6 ) 50.5(12) NarCOi 5 0 . 5 ( 8 ) 5 6 . 8 ( 6 ) 5 7 . 5 ( 6 ) 8 5 . 2 ( 6 ) 4 7 . 6 ( 6 ) 50 5 ( 1 2 ) Modifiedsoda 5 1 . 0 ( 1 0 ) 5 4 . 8 ( 4 ) 5 8 . 5 ( 8 ) 8 3 . 9 ( 8 ) 4 4 . 5 ( 8 ) 48 4(12) NaaPOa:12HaO 5 9 . 2 (10) 6 0 . 2 (8) 6 2 . 5 (8) 8 6 . 5 (8) 4 8 . 0 (8) 45 3 (12) Naz0.3.25SiG 7 3 . 4 (8) 6 4 . 8 ( 1 2 ) 6 9 . 4 (10) 9 1 . 0 (12) 5 4 . 2 (10) 49.3(141 Figures in parentheses show number of readings averaged. This twice t h e number of samples, as one reading was made on each side of cloth. T a b l e VI-Effect
k
Fipure 5--DopEIBifion of Soila on Cotton Sheeting From Siliraie Soluiion From Wafer Ii-Dust from Philadelphia building M-Same dart BE 1, N-Mica 0-Mica
Figure &Deposition of Carbonaceous Piaments on Cotton Sheeting
P-tiltramaiiSe
*ultramarine
(Due to lack of renriti\%fy t o blue of ordinary photographic piate. the runtlast betreen P and Q is nos adequately shown)
Co~.l.orus~-Ttic~utstimdingdifference between silicate and the other liiiilders used iii the foregoing tests is t h e eolloidal character of the silicate. I'liospliste, which has sonic colloidal diaracteristics, was more eflective thaii the rest of t,lic builiiers. It. therefore s e e n i d desirihle to sce what eRect colk,iris would have, either alrilie or in the presenn. of alkalilie materiak. Sols of niiiinal glue, gum arabic, colloidal clay, and wheat-starch paste werc prepared arid mixed with pigment were rotated with strips of clean clntli, ils in the earlier of the preceding series. Termilion was omitt.ed.
Ten milliliters of a suspension of 1 gram of colloidal clay* in 200 mi. of water had little if any cffed. In the presence of sodium carbonate it gave some protection. This may have been due to tile formation of a littlc silicate. since hydrous silica is soluble in sodium carbonate solutioiis. The starch sol was prepared by heating 1 ram of wheat starch in 200 ml. of water until the starch was swollcn. The mixture was then cooled. When thc tests in Table 111 were RDeatcd with the addition of 10 mi. of the starch sol. the effect was not appreciable. Howcver. nrhen the b a r method was used, the results given in Table VI1 were ohtained. With the larger amounts of pigment the vffects of the starch were evident. With ferric oxide and burnt limber the alkaline starch sols did reduce deposition, but with yellow ochrrfhey did n o t
One gram of hide glue was dissolved in 200 ml. of water, and 10 ml. were used in ctxh test. Samples were run both with and
Tablo YII-Addidon of Starch fa Alkaline Bviiders (Peiceiliage of whiteness compared with original cloth)
without sodium carbonate present. The glue alone gave a little protection, hit this was destroyed by the addition of carbonate.
a
Pigiiies in rmenfhescs rhos number or ieiidiner made and ayerased
to ohiain figtires they
Figure 6- Deposition of Pigment8 on Cotton Sheeting From siiicnte Solution Prom water K-Yellow ocher S--Yellow orher T-Raw umber ti-Raw umber V-Burnt umber W-Burnt umber X-vermilion Y-WrmiIion
Gum arabic, used uridcr the same conditions, was without effect alone. The addition of sodium carbonate had no effect with raw umber, and an adverse one with burnt umber and yellow ocher. With ferric oxide, however, the combination gave some protection.
follow.
None of the mixtures tried were as effective as Na20:3.25SiOl. Colloids alone did not seem to give much protectiori, hut, when alkalinity was coupled with colloidal properties, mine protection u'as given. DIFFERENTSODIUM SILICATES-Aseries of tests was run with silicate solutions, ranging in ratio from NaaO:SiO;! to K%20:S.RBSiOz. Each was used at such dilution that the total KasO u'as0.046 per emit. The same pigments were used as in the preceding series with strips of cloth. The silicates used were IYa,0:3.86Si02, Naz0:2.84Si02, KatO:2Si0, NazO.1.58SiOr, and the defiriitely cryst.al1ine inetasilicate-RaSiOs with some water of crystallization. All of these gave results like those obtained with Na20:3.25Si02, i. e., the pigments were IarKeIy prevented from becoming attaclied to the cloth. (See Figures 11 and 12.) The met.asilicate, except with yellow ocher, was somewhat less effective than the other silicates. These tests emphasized the fact which was brought out by the tests with the other alkaline builders, that the protective effect was not dependent on the total NitzO. They did indicate that the total SiOt was an important factor, since the :"Gelacov obtained from Hammil and Gillelpie.
INDUSTRIAL AND ENGINEERING CHEMISTRY
December, 1931
Table VIII-Protective CONCN.OF Sal0
AMOUNT Si02 AND
%
%
0.0345
SiOn Whitenessc si09 Whitenesse Si02 Whitenessc
WHITENESS
0.0230 0.0115
Naz0:1.58SiOn
Nar0:ZSiOr
Naz0:2.84SiOz
Naz0:3.25SiOz
0.054 90.4 0.036 90.4 0.018 91.8 0.0072 87.0
0.0675 98.6 0,045 89.7 0.0225 89.4 0.0092 83.6
0.098 93.2 0.065 91.8 0.0225 95.9 0.0130 90.4
0.112 86.3C 0.075 91.8 0.0375
0.0334 90.4 0.0223 90.4 0.0111 87.7 0.0045 80. I C
0.0111
82.2 0.0045 83.6
Si02
0.0046
Effect of Various S o d i u m Silicates a t Different Dilutionsa (Umber on cotton cloth)
NazSiOs 1st series 2nd series6 0.0334 89.0 0.0223 89.0
1393
Naz0:3.86SiO1
0.132 92.5 0.088 91.8 0.044 d 95.9 0.0150 0.0177 90.4 94.5 0.00885 84.2a The five samples were 68.5, 71.2, 71.2, 72.6, and 74.0
Whitenessc .... Si02 .... Whitenessc a Water alone gave an average whiteness equal to 71.5 per cent of that of the original cloth. per cent. b This series was run with the second lot of umber which was more yellow and did not give as satisfactory results in the photometer. c Based o n original whiteness of cloth. d This sample was unevenly colored probably by sticking in the cover of the jar during part of the run.
.... ....
.... ....
0.0023
metasilicate solution with only 0.044 per cent SiOz was decidedly less effective than the others in which the silica varied from 0.073 to 0.177 per cent. To determine the effectof different concentrations of silica, another series was run at different dilutions. The results are given in Table VIII. It will be noted that there are actually two series represented. The second was run when it Fas discovered that the first needed some extension. Unfortunately in the meantime all the original umber had been used so that the second series was on a different lot. A comparison of the readings for the two sets of metasilicate samples indicates that this made very little difference. It will be observed that the protective effect seems to be dependent on the silica content. At concentrations below 0.01 per cent the protection is greatly reduced, although even 0.0045 per cent Si02 is decidedly better than water alone. Still another series was run, using ferric oxide, yellow ocher, and burnt umber with the cloth in the form of bags. Solutions of NasSiOs and Na20:3.25Si02were prepared so that they had exactly the same silica content. This meant that the metasilicate solution contained three times as much NanO as the other solution. The results (Figure 13) show that this made very little difference. The protective effect was produced by 0.02 per cent, or more, SiOp without regard to the NazO content. Redeposition
EARLY TESTS--~ series of washing tests was made to study redeposition. The soiling mixtures used were based on the 100%
90
80
,
BUILDER IN DETERGENT 70
60
50
40
30
20
.... ....
.... ....
....
....
one then standard with the Detergents Committee of the American Oil Chemists Society. These contained 10 grams of wheat starch, 0.6 gram of gum tragacanth, 2 grams each of edible tallow and h’ujol, and 82.4 grams of distilled water. In addition, 3 grams of carbon black or G of either manganese dioxide or raw umber were added. One lot was made with umber in which the fatty materials were omitted. The mixtures were heated until the starch swelled and then were allowed t o cool before application t o the cloth. They had a pasty consistency when finished which permitted them t o be printed on Utica sheeting with a rubber stamp. Unfortunately the soiling mixture squeezed between the threads and beyond the stamp so that it was not evenly distributed, and the outline was blurred. Each piece of cloth was placed in a jar with 100 ml. of one of the detergent solutions described in the paragraph on “Other Soils” and ten rubber balls about 3/g inch (0.95 cm.) in diameter. The jar was then rotated in the launderometer for 20 minutes a t GOo C. The pieces were then removed and centrifuged in the basket of a laboratory centrifuge. They were rinsed twice-10 minutes each time-with 200 ml. of distilled water, and centrifuged after each rinse. The samples were examined, and the process was repeated. After the twenty-first cycle (twentyone washes and forty-two rinses) the marks were not completely removed in any case, but the tests were discontinued because the removal had become extremely slow.
Soap was best for removing the printed marks, but it did not protect the portions which were originally unsoiled as well as did silicate. Mixtures of the two seemed to combine the good properties of both. Manganese dioxide, probably owing to coarser particles, was more readily removed than the other pigments. This series showed very clearly that redeposition was important, and that the best detergent for removing dirt B U I L D E R I N DETERCENT
IO
0
sslW%
90
80
70
60
50
85
I
40
.J O
2U
IO
I
I
I
0
I
~
I
A
I
/
\ I
\
I
I
I
I
1
I
50
Figure 7-Deposition
of Ferric Oxide on C o t t o n C l o t h w i t h Various D e t e r g e n t Solutions
Figure 8-Deposition
of B u r n t U m b e r on C o t t o n C l o t h w i t h Various Detergent Solutions
_____--
power was measured.
~~
________
Table IX-Reflecting
OIIOINAL
CLora
mBx20wAsWIN0 CYCLBS WITH:
(a) water
(b) 0.2% d n . Ff Na~0:3.256Ch (C)
0.2% Id". of rwliumoleate
(d) 4 parts of (h) with 1 of (c! (e) 1 part of
(b!
with 201 (E)
Sone m DZTEPTZNT
W v r e %--Deposittonof Yellow Ocher on C u f t o n Cloth w i f h Various Detersent Soluflons -tm4
W
Bo
..
E &$
I
70
auriDCR m DcTcReENr
60
.... ~.
I I
I
50
I
__
a0 ~
34
20
3 0
,.- _,
kdj
..
Power of Washed Sheeting wifh Dlfferenf Soillna Miltfume FBXBIC 0XlDli
Un-
R*W
uarsen
BURNT UYBHIL
Cresoli BLICK
u..
Un-
UXl-
Soiled soiled Soiled soiled Soiled soiled Soiled soiied
79
83
70
88
75
86
71
83
83
90
Si
93
78
91
85
92
87
91
83
91
80
95
87
94
88
95
81
95
77
94
88
94
87
93
80
92
83
95
87
82
I n this series it is evideut that the silicate solution has marked removing and protecting powers but not quite BS great as those of the soap solution. The silicate is relatively better as a protecting than as a removing agent. The first series was more favorable to silicate but, as will be shown in a later article, this may have been due to the presence of carbon dioxide in the water' Mixtures of soap and silicate were as good or slightly better than either one alone, since they combined the abilities to remove and protect,
- .
I
_j
0
The results are given in Table IX.
Basis of Protective Action
EFFECT ON ~ r a ~ l s ~ i ~ s ~ pigments - - T h e used in the washing tests were riven a nreliminarv treatment with Nav0:3.86SiO,. For this purioose 0.05 giam of each pigment was snspended in 25 ml. of water and then mixed wit.h 100 rnl. of &ate solution, contaming 0.040 per cent Ea&, for 1 hour a t 60" C . The pigments were then allowed to settle, and the clear liquids were removed by siphoning. This showed plainly that the p i p e n t s were not thoroughly deflocculated
Plaure l&Depoaition
of Carbon Black en C o t t o n Cloth with Various Detergent Soiuflona
was not necessarily the most efficient in preventing its transfer to clean portions of the cloth. SECOND SERIES-A second series of tests was run in which the soiling solution was applied evenly over a considerable area of cloth so that it was possible to measure the degree of removal by photometric means. In this series the soiled cloth was washed together with an unsoiled cloth. I n some cases a portion of the soiled piece was left clean. Examination of the samples indicated that it made no difference in the results whether the soiled portion was attached or not. This would indicate that the pigment did not transfer by means of capillary attraction. Since In the first srries the oil in the soilimg mixture did not seem nearly as difficult to remove &s the pigment, it was omitted in this series. More aater was added to make the mixture workable. It thus became: 0.6 &ram tragacanth, grams wheat starch, 20,0 grams pigment (except carbon black, of which only 5 grams were used), and 250.0 grams water. This mixture was applied by passing a dry strip of cloth through it. The excess was scraped off and the rest allowed to dry. Each strip was washed in the launderometer with 100 ml. of detergent solution and ten rubber balls for 20 minutes st 60" C. Then followed two rinses of 5 minutes each with 100 ml.
PiBure
(sx
of Sodivm Silicates of Diff~erenf Rafios on Depodfio" Of Pigmen$* left wlih yenow ocher end sir on right wlih burnt umber! &Nan0 3 855*0% B-NarO 15SS10, K-N-0 2 84SQ M-NarSzO. C-NmO 2SzU w-water alone
by this concentration of silicate. When the treated pigments were placed in 100-ml. portions of water and rotated in the launderometer as before with clean pieces of cloth, i t was found that the silicate treatment had prevented the deposition of pigment to some extent, except with raw umber (see ~i~~~ 14). attemptto repeatthis with new pigments Was ~nsuccessfulbecause the piments were too thoroughly deflocculated to settle.
December, 1031
INDUSTRIAL AN I) ENGINEERING CHEMISTIZY
EFFECT ON CLOTH-A parallel series uf experirricnts was run, in which pieces of cloth were treated with silirate before bringing them in contact with the pigments both by the strip and bag methods. In every case the colors were much paler
Figure &%---Effect of Sodium S l l l ~ a f e of s Dlffrrcnf Rados en Deposinon of Pigments on kit are with TBW umber and six en ri,%htwith ferric oxide.
six
1395
thesilicate, it was found thatits protective eflect prugreaively decliiied as neutralization proceeded beyond 75 per cent to completion. When a solutivn of Na2C0,, containing 0.046 per cent NanO, was progressively substituted for the NazO:-
F1~urel+Prevenflon
of Depodfian by Treatment of Figment and Cloth
Letters repicrent same silieafrr a3 xn Figure 11.
than those in whicli the cloth was untreated or in which the pigments were treated. These tests indicated that the action on the cloth was the primary factor in preventing deposition. The formation of an exceedingly thin film on the cloth would be a logical explanation of the results observed (see Figure 14). DEsTnuCTioN OF PROTECT~TE AcTiox-The film hypothesis is supported hy the fact that the protcctive effect may be greatly redrieed or destroyed by soaking the treated pieces in two portions of either hot or cold water, or by drying the treated cloth at room temperatures. When the treated cloth was washed for 5 minutes a t 60" C . with 100 ml. of any of the
3.84Si0, solution, a definite decrease in protection was found as the proportion of carbonate increased. So far efforts to learn the composition of the film on the cloth bave not been successfnl. Laundering Advantage
In the iaundry wash wlieel not all the load is uniformly soiled. Even in the Iiousehold washing machine some clothes are much dirtier tlian others. I n either case the presence of silicate in the detergent solution is an advantage, not only as an emulsifying agent. (6) but as a, preventative of redeposition. This will be discussed more fully in a later article. Redeposition is, of course, only one of the factors in the selection ofa detergent, but i t is an iinport.mt oue which s e e m to he worthy of more consideration than it has received in the past. Literature Cited (1) Appei, Smith, and Chrirdron. Pro'. A m . Assocn. TmIila Chcm. Coloriris. 19a8, 265; ~ m ~ . ~ e ~ Ri ~ uP I T f . ,IT. 731 (1928). ( 2 ) Chapin, Oil For Ind., 6, 95 11928). (3) de Kcghel. Ra. rhim. id,20, 171 11921). (4) Rhodes and Brainerd. IND. E N U . Cnt.r., 21, 60 (1929). (5) Spring, Rrc. troa.
