INDUSTRIAL AND ENGINEERING CHEMISTRY
June, 1942
L
latent heat of vaporization, B. t. u./lb. molecular weight pressure, Ib./sq. in. abs. vapor pressure, lb./sq. in. abs. reference vapor pressure, lb./sq. in. E‘‘ residual vapor pressure, Ib./sq. in. R universal gas constant T temperature, R. (” F. 459.69) t l = temperature, F. V = specific volume, cu. ft./lb. = residual specific volume, cu. ft./lb. 2 = compressibility factor, PV/bT M P P” P$
= = = = = = = =
O
+
Subscripts 0 = reference state b = bubble point d = dew point
Superscript * = infinite attenuation
737
Literature Cited (1) Budenholzer, Sage, and Lacey, IND. ENQ.CHEM.,31,369 (1939).
Cailletet and Mathias, Compt. Tend., 102, 1202 (1886). Griffiths and Awbery, Proc. Phys. Soc. (London), 44, 121 (1932). Kennedy, Sage, and Lacey, IND. ENQ.CHEM.,28,718 (1936). Konz and Brown, Ibid., 33, 617 (1941). Lewis, PTOC.Am. Acad. Arts Sci., 37,49 (1901). (7) Pattee and Brown, IND.ENG.CHEM.,26, 511 (1934). (8) Pitzer, J . Am. Chem. Soc., 63,2413 (1941). (9) Rose-Innes and Young, Phil Mag., [5] 47,353 (1899). (10) Sage, Backus, and Vermeulen, IND.ENQ.CHEM., 28,489 (1936). (11) Sage, Evans, and Lacey, Ibid., 31, 763 (1939). (12) Sage and Lacey, Ibid., 32,992 (1940). (13) Sage and Lacey, Trans. Am. I n s t . Mining Met. EngTs., 136,136 (1940). (14) Sage, Schaafsma, and Lacey, IND.ENQ.CHEM.,26, 1218 (1934). (15) Sage, Webster, and Lacey, Ibid., 29, 1188 (1937). (16) Ibid., 29, 1309 (1937). (17) Timmermans, Sei. Proc. Roy. Dublin Soc., 13,310 (1912). (18) Young, Ibid., 12,374 (1910). (2) (3) (4) (5) (6)
Value of Silicate of Soda as a Detergent HARRY L. BOLTON Philadelphia Quartz Company, Philadelphia, Penna.
The ability of silicates, phosphates, borax, soda ash, and caustic soda to reduce the amount of soap required to form “permanent” suds in hard water has been investigated. The more alkaline silicates, caustic soda, and the phosphates resulted in greatest soap economy in the concentration range of 0.1 per cent or less. Caustic soda and soda ash produced large adherent soap curds which were difficult to disperse. Any curds developed with the eilicates or phosphates were very minute and so well dispersed that they were apparent only as turbidity.
T
H E average housewife adds enough soap to her dishpan t o make a good suds; so does the laundryman to his wash wheel. Despite much study of the various factors involved in detergency, it is still a fact that in most washing operations the minimum soap requirement is that neceesary to maintain a satisfactory suds. Alkalies can be used t o reduce the amount of soap required in many cases. Individually they differ a great deal in their behavior in hard water, toward various types of soil, at different temperatures, and with different soaps. A full comparative evaluation of the alkalies as “soap savers” through their ability to reduce the amount of soap required to make a satisfactory suds cannot be made from published data. I n view of the many complicating factors involved, this is not surprising.
Effect of Silicates, Phosphates, Borax, Soda Ash, and Caustic Soda on Oleate and Stearate Soap Requirements for Sudsing in Hard Water Previous papers in this series (2, 3, 6) and others (4) allow some comparison of the alkalies as detergent aids. I n all of them the comparison is based on the results of complete washing tests. I n the present work a procedure was developed whereby the comparative effectiveness of the alkalies as soap savers in hard water could be studied under certain fixed conditions. (For convenience the term “alkali” is considered as including the polyphosphates.) The work was limited to a study of the effect of the alkalies on sodium oleate and sodium stearate requirements, a t 20” and 60” C., respectively, for sudsing in water containing 300 p. p. m. calcium carbonate equivalent hardness, one third of which was present as magnesium salts. Caution should be exercised in applying, without experimental confirmation, the findings of this work to other detergent problems under different conditions.
Water, Soap, and Alkali Used Measurements were made of the soap required to give a “permanent” suds in a hard water to which had been added a small amount of alkali. The technique was a modification of that recommended by the American Public Health Association and the American Water Works Association ( I ) for the determination of hardness. In the interest of controlled conditions a synthetic hard water was used. A stock solution containing 600 p. p. m. (35 grains per gallon) calcium carbonate equivalent was prepared by dissolving 1.8105 grams of 73.5 per cent calcium chloride and 1.2180 grams MgC12.6HzO (both salts were c. P. grade) in 3 liters of distilled water. The ratio of 2 to 1 in
738
FIGURE 1. SODIUM OLEATEAND SILICATE (ANHYDROUS) REQUIRED FOR PERMANENT SUDS IN 100 ML. O F HARDWATER (300P. P. M. CaC03 EQUIVALENT) AT 20” C.
terms of calcium carbonate for calcium and magnesium was chosen as best representing many natural waters. Some supplementary tests were made with a water containing the same equivalent hardness present as sulfates. With both types of water the stock solutions were diluted with distilled water and additive solutions to reduce the hardness to 300 p. p. m. (17.5 grains per gallon) for the actual tests. In order to eliminate as many unknown variables as possible, two pure soaps were used. Sodium oleate (Merck’s neutral powder, C. P. grade) was used at 20” C., and sodium stearate (Baker’s U. S. P. grade) a t 60” C. A 1.0 per cent water solution of each soap was prepared and held in a thermostatically controlled water bath which maintained the desired temperature within the limits of *0.25” C. The stearate solution formed a stiff jelly a t room temperature, but a t 60” C. it became homogeneous and could be handled satisfactorily. With the exception of the caustic soda which was a c . P. grade, the alkalies used were commercial products. All are listed below in the form in which they were used. The Calgon was the “adjusted” product contajning a small amount of sodium carbonate: Material “S” brand (sodium silicate) “N” brand (sodium silicate) ”K” brand (sodium silicate) “U” brand (sodium silicate) “C” brand (sodium silicate) “B” brand (sodium silicate) “Metso” (sodium metasilicate) “Metso 99” (sodium sesquisilicate) Caustic soda (sodium hydroxide) Borax (sodium tetraborate) Soda ash (sodium carbonate) Trisodium- phosphate Tetrasodium pyrophosphate Sodium tetraphosphate “Calgon” (sodium hexametaphosphate)
Composition NazO .3.9SiOn (30.9% soln.) NazO .3.2SiOa (37.6% soln.) NazO . 2.9sioz (42.9% soh.) NazO .2.4SiOe (46.9% soh.) NazO .2.0Si02 (54.0% Soh.) KaSO . 1.6SiOz (62.9% soh.) NarSiOs.6H20 NaaHSiOa.5HzO NaOH NazBiOi.lOH20
NasPsOls
Stock solutions of each of these materials with the exception of the tetraphosphate and Calgon mere made up and stored. The two phosphate solutions were freshly prepared each day as needed.
FIGURE 2. SODIUM OLEATE AND ANHYDROWE, ALKALIREQUIRED FOR PERMAXENT SUDS IN 100 M:L. OF HARD WATER (300 P. P. M. CaCOI EQUIVALENT) AT 20” C.
Experiments with Hard Waters
A 25-ml. portion of the synthetic hard water was measured by pipet into a 250-ml. narrow-mouth glass bottle. The required volume of alkali solution mas added from a buret, the final volume adjusted t o 50 ml. with distilled water, and the mixture brought to the desired temperature by immersion in the water bath. Soap solution was added from a 10-ml. graduated pipet. The bottle was shaken vigorously after each addition of soap and returned t o the bath in a horizontal position. When a persistent suds was produced, an electric stop clock was used to measure the time it remained intact over the entire surface of the solution. A second stop clock measured the total elapsed time for the soap titration. A permanent suds (defined as one lasting for 5 minutes) was considered the end point. Care was taken to avoid confusing the socalIed fahe or magnesium end point with the true end point. From the total volume of soap solution used, the weight of real soap required for 100 ml. of hard water was caIculated. With the completion of each titration the solution was brought to room temperature (20-25’ C.) and a colorimetric pH determination was made using a W. A. Taylor slide comparator. The volume of the sample a t the end point was necessariIy increased by the addition of soap solution. However, this increase in volume was considered of little importance hince the change was due entirely to distilled water. The final results appeared to be influenced slightly, if at all, by the time required for the titration even a t the higher temperature. This was of especial interest in the case of the pyrophosphate and the two polyphosphates, all of which are known to revert in some degree t o the orthophosphate in hot alkaline solution. Three separate sets of determinations were made: (a) All of the alkalies were run with sodium oleate at 20” C. in water containing the hardness as chlorides; (b) the same materials were run with sodium stearate a t 60” C., using water containing the hardness as chlorides; and IC) sodium metasilicate and tetrasodium pyrophosphate were run with sodium oleate a t 20” C. in water containing the hardness as sulfates. The alkalies were used in concentrations of 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.15, 0.20, 0.25, 0.30, 0.40, and 0.50 gram per 100 ml. of solution. In an abridged form the data on soap requirements are given in Tables I and 11. For convenience, all of the alkali concentrations are given on the as-weighed basis. I n order
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
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739
SODIUM STEIARATE AND SILICATE (ANHYDROUS) RE- FIGURE 4. SODIUM STEAR.4TE AND ANHYDROUS ALKALIREPERMANENT Sms IN 100 ML. OF HARDWATER QUIRED FOR PERMANENT SUDS IN 100 ML. OF HARD WATER (300 P. P. M. CaC08 EQUIVALENT) AT 60" C. (300 P. P. M. CaC08 EQUIVALENT) AT 60' C.
FIGURE 3.
QUIRED FOR
t o present a fair comparison, however, the results with the hydrated materials were calculated to an anhydrous basis €or graphical representation (Figures 1 to 5, inclusive). It is necessary that this be kept in mind when comparing the tables and charts, for in many cases some correction for water must be made before correlation is possible. With sodium oleate a t 20" C. in the chloride water the silicate results (Figure 1) varied in the same general order as the ratio of Si02 to NazO; i. e., the lower the ratio, the lower the soap requirements. However, three members of the group, NazO.2.4Si02, NazO. 2.0Si02, and Na2O. 1.6Si02 gave results so nearly identical that only one curve could be drawn for the three. This behavior was also apparent in the work with sodium stearate at 60" C. (Figure 3). I n this case one curve adequately represents the results with NanO. 2.4SiOn and Ka2O. 1.6Si02, but the intermediate member, Naz0.2.0Si02, gave appreciably different values. The same similarity of results was found with sodium tetraphosphate and Calgon in Figure 2 where one curve is shown for both materials. Here, also, the data for soda ash are not completely represented because of an indicated minimum between the concentrations of 0.10 and 0.15 gram per 100 ml. which could not be properly shown on the scale best suited to the other curves. However, the values for this material listed in Table I indicated the extent of the break in the curve. I n most cases minor inflections and change of direction are believed due to experimental error and were neglected. It is possible, however, that major irregularities, as in the case of the soda ash, may have real significance. (Later work will check this point.) ' All of the curves of Figure 4 are well defined and, in moet cases, show appreciable differences in results obtained with the various materials. In the work with sulfate water, only sodium metasilicate and tetrasodium pyrophosphate were used. The curves of Figure 5 represent the results. The original soap data were believed reproducible within =t 0.005 gram per 100 ml. The maximum discrepancy in soap values with zero alkali concentration was 0.011 gram, but the average was considerably less. While most of the values reported in the tables were the results of single determinations, duplicate and, in one case, triplicate determinations were made of a number of points. As an example, with concentrations of 0.00, 0.06, 0.07, 0.08, 0.09, and 0.10 gram per 100 ml. of pyrophosphate, the pH values and sodium oleate
FIQURE 5. EFFECT OF CHLORIDES AND SULFATES ON AMOUNTS OF SODIUM OLEATEAND ANHYDROUS ALKALIREQUIRED FOR PERMANENT SUDSIN 100 ML. OB HARDWATER(300 P. P. M. CaC08 EQUIVALENT) AT 20" C.
requirements a t 20" C. as originally determined and as checked after a period of several weeks were: Original Result Oleate, gram
pn
Check Result Oleate, gram PH
Additional checks with soda ash, trisodium phosphate, metasilicate and caustic soda indicated a similar degree of reproducibility. All pH values (Table 111) were determined by the colorimetric method. The values cannot be expected to agree exactly with results obtained by different methods, but they are useful and informative. The value of such data will be apparent t o workers in the field of detergency where the importance of pH has long been recognized.
Relative Efficiency of Alkalies If a comparison is made of the amount of sodium oleate required with an alkali concentration of 0.10 gram per 100
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Vol. 34, No. 6
required amount of oleate. In the low concentration range caustic soida produced a greater reduction in required soap than any other alkali, either silicate or otherwise. However, Grams of Soap a t Alkali Concn. of: in every case the caustic produced large, ad0.00 g. 0.01 g. 0.03 g. 0.05 g. 0.10 g . 0.20 g. 0.30 g. 0.50 g . Alkali herent soap curds which were not easily broken Sodium Oleate (20' C.) up or dispersed. These appeared almost imNazO .3.9Sioz (30.9% mediately after the solution was mixed and 0.216 0.212 0.208 0.193 0.158 0.134 0.225 0.224 soh ) grew, both in size and in number, with time. NazO .'3.2SiOz (37.6% 0.235 0.235 0.224 0.218 0.202 0.162 0.136 0.133 soln.) Figure 6 shows the relative size and tenacity NaZO. 2.9Sioz (42.9% 0.227 0.220 0.214 0.202 0.175 0.131 0.128 0.124 of the curds after standing long enough for the soln.) NazO, 2.4SiOn (46.9% suds to disappear. The "bath tub ring" and 0.226 0.216 0.204 0.197 0.167 0.129 0.124 0.133 soln.) NazO .2.OSioz (54.0% coagulated condition developed with the 0.224 0.213 0.203 0.192 0.154 0.132 0.124 0.112 soln.) NazO. 1.6Sioz (62.9% caustic soda can easily be seen. 0.132 0.128 0,117 0.226 0.212 0.200 0.190 0.154 soln.) 0.232 0.202 0.180 0.164 0.144 0.134 0.131 0.128 In the experimental work these same effects Na~SiOa.5Hzo 0.135 0.125 0.126 0.144 0.140 0.160 0.211 0.232 Na~HSi04.5HeO were apparent with soda a6h although they 0.235 0.19s 0.131 0.137 0.135 0.135 0.134 0.136 NaOH 0.227 0.234 0.230 0.234 0.232 0.237 0.241 0.248 Na~B~Ov.1OH~O were not so marked. 'With all other alkalies, 0.226 0.212 0.212 0.166 0.104 0.188 0.135 0.088 NazC08 especially the silicates, the soap curds de0.228 0.228 0.211 0.206 0.186 0.082 0.080 0.061 NasPOi.12HsO 0.120 0.101 0.113 0.144 0.133 0.226 0.190 0.168 NaaPlOi veloped were so fine and so well dispersed as 0.226 0.216 0.175 0.157 0.120 0,089 0.006 0.003 NasPaOia 0.227 0.219 0.177 0.160 0.116 0.088 0.034 0.068 NasP~Oia t o be apparent only as turbidity which was quite stable. The uniform appearance of the Sodium Stearate (60° C.) metasilicate solution in Figure 6 ia representaNazO, 3.9Sioz (30.9% 0.208 0.205 0.205 0.203 0.197 0.185 0.181 0.177 soln.) tive of this condition; the value of deflocN m O . 3.2Sioz (37.6% 0.207 0.205 0.201 0.201 0.191 0.177 0.174 0.140 culating power was wel!l demonstrated. N:$:)2.9Sioz (42.9% 0.207 0.203 0.201 0.193 0.179 0.172 0.156 0.123 The Calgon and tetraphosphate were effecsoln ) NazO .'2.46iOz (46.9% tive with the oleate (Table I) but were in0.207 0.203 0.197 0.185 0.174 0.170 0,130 0.118 N,8$?2.OSiO2 (54.0% ferior t o several of the other materials in the 0.208 0.204 0.193 0.189 0.168 0.152 0.130 0.120 soln ) NazO .'1.6SiOz (62.9% stearate work. Both of these polyphosphates 0.208 0.203 0.193 0.177 0.164 0.144 0.124 0.120 soln 1 approached maximum efficiency a t concentra0.209 0.199 0.168 0.152 0.140 0.135 0.128 0.124 NazSiOs.5H20 0.207 0.199 0.170 0.158 0.137 0.128 0.122 0.120 NasHSiOa.5HzO tions in excess of 0.20 gram per 100 ml. In 0.156 0.116 0.191 0.168 0.118 0.120 0.118 0.207 NaOH 0.207 0.205 0.203 0.203 0,199 0.199 0.195 0.193 contrast, the pyrophosphate appeared to best NalBa07.10HzO 0 , 2 0 5 0.201 0.185 0.188 0.183 0.185 0.187 0.188 NazCOs advantage a t low concentrations and, on st 0,205 0.201 0.199 0.195 0.189 0.187 0.183 0.181 NasPO4.12HaO 0.205 0,205 0.197 0.175 0.130 0.124 0.122 0.122 NacPzOi comparative basis, produced good results with 0.148 0.189 0.163 0.136 0.156 0.205 0.205 0.166 NarPaOia 0.207 0,207 0.199 0.194 0.166 0.154 0.177 0.168 both soaps. Surprisingly low soap requireNasPsOis .~ ments were obtained with trisodium phosDhate in the work with sodium oleate. but this salt appeared to have little value 'with ml., the silicate curves are well grouped from about 0.13 to the stearate. It is of 0.14 gram of soap per 100 ml. Several of the intermediate interetit that the metagrades are somewhat superior to the metasilicate and sess i l i c a t e , sesquisilicate, quisilicate, although a t lower concentrations this is not the and caustic, in addition case. With the stearate the spread between the various silit o the pyrophosphate, cates is much greater, and the two crystalline members were the only alkalies (metasilicate and sesquisilicate) are markedly superior over giving consistent results almost the entire range. Although the sesquisilicate is the with both soaps and both most alkaline of the series and, in general, gave best results temperatures. under these conditions, the decrease in soap consumption From further considwith 3Naa0.2SiOz as compared to that with NaZO.3.9Si02 is eration of the curves not in proportion to the difference in alkalinity of the two of Figures 1 t o 5 some materials. indication of the econThe alkalies other than the silicates gave different results omy a n d increased under the two conditions. Borax decreased the stearate reteff e c t i v eness possible quirement only slightly and actually caused an increase in the through the use of the alkalies may be demonstrated. The broken TABLE11. EFFECTOF CHLORIDES AND SULFATES ON SODIUM line as shown on the OLEATEREQUIRED FOR PERRIANEXT SUDS I N 100 ML. OF HARD charts represents what WATER(300 P. P. M. CaCOaEQUIVALENT) CONTAINING A FIXED might be thought of as AMOUNTOF ALKALI the curve which would (Temperature 20° C.; colorimetric p H measurements made a t room temDerature. 20-25' '2.1 have been obtained had Sodium Metasilicate Tetrasodium Pyrophosphate the soap been used as Alkali Chloride Water Sulfate Water Chloride Water Sulfate Water one of the alkalies. Then Conon.. Soap, Soap, Soap, Soap. Gram gram pH gram pH gram pH gram pH any portion of another 9.7 0.247 8.9 0.226 8.5 0.242 0.232 0.00 curve falling below this 0.190 8 . 3 9 . 9 0.218 8 . 9 0.224 4:s 0.202 0.01 8.5 0.165 line represents mixtures 8.8 FIGURE6. COMPARISON OF 1 0 . 5 0.168 0.202 11.3 0.180 0.03 0.152 0.144 9.1 8.3 10.7 0.168 11.4 0.164 0.05 CURD DEVELOPMENT WITH of soap and alkali which 9.4 10.9 0.138 0.133 9.5 0.144 0.155 11.7 0.10 METASILICATE(RIGHT-HAND 11.3 0.123 0,120 9 . 5 9.7 0.141 11.9 0.134 0.20 would be expected to be 9 . 8 0.116 0.113 9 . 7 11.3 TUBE) AND CATSTIC SODA IN 0.139 11.9 0.131 0.30 more effective on a 9.8 0.104 0.101 9.9 11.3 0.136 12.0 0.128 0.50 HARD w.4TER SOLUTION CONpound for pound basis TAINIKG SODIUM OLEATE
c
TABLE I. SODIUM OLEATEOR STEARATE REQUIRED FOR PERMANENT SUDSIN 100 ML. HARDWATER(300 P. P. M. CaCOa EQUIVALENT) CONTAINING A FIXED AMOUNTOF ALKALI
June, 1942
I N D U S T R I A L A N D E N G I N E E R I N ~ GC H E M I S T R Y
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Discussion and Conclusions
TABLE 111. COLORIMETRIC pH VALUES FOR HARD WATRR SOLUTIONS CONTAINING ALKALIAND SODIUM OLEATEOR STEARATE AT ROOMTEMPERA-
The problem of detergency is complex, and only one phase of it is covered by this work. I n most cases, however, sudsing ability is one p H Values a t Following Alkali Concn. in Q./lOO MI.: Alkali 0.00 0.01 0.03 0 . 0 5 0.10 0.20 0 . 3 0 2 . 0 . 5 0 of the essential requirements of a good detergent solution containing soap. I n this respect Alkali and Sodium Oleate the high comparative efficiency of the more 9.1 9.4 9.7 10.3 10.5 10.5 8.8 8.9 Na2O. 3.9SiOz 3 0 . 9 7 s o h ) alkaline silicates as soap savers at low concen9 . 8 10.3 10.3 1 0 . 3 8.7 8.7 9.3 9.4 NazO 3.29102 37 6 mln.) 8.8 9.4 9.3 9.6 9 . 8 10.5 10.5 10.5 NazO :2.9S+ / 4 2 : 9 8 s o h ) trations in hard water may be of real signifi8.7 9.1 9.5 9 . 6 10.4 10.5 10.5 10.5 NazO 2.4SiOz 46 9 7 s o h . ) NarO 2.05!02 (5410% s o h ) cance in washing operations. Under condiNazO NarSiO?.5HzO . 1.6910~(62.9% s o h ) tions similar to those of these experiments NasHSi04.5HzO the use of the relatively expensive sequesterNaOH ing agents would seem to offer little advantage NazB4Or. lOH2O for developing permanent suds, since the NasPO4.1ZHz0 NazCOa NaaPtO7 8.5 8.3 8.5 8.3 9.4 9.5 9.8 9.8 silicates are more effective and can be used in 8.3 8.9 8.3 8.2 7.9 8.1 8.3 8.2 NasP401a hard water without undesirable results. NasPdOla 8.6 8.7 8.4 8.2 7.9 7.9 7.6 7.8 Although the silicates do not prevent preAlkali and Sodium Stearate cipitation of the hardness in water, the inV a t 0 3 9SiOz 30 9 % soln.) 8.5 9.0 8.9 9.1 9.4 9.5 9 . 7 10.3 soluble curds formed are so well dispersed as ka2O :3:2Si02 /37:601 s o h ) 8.5 8.5 8.5 9.3 9.6 9.7 9.7 10.3 to cause no difficulty. I n this connection it NazO 2 9SiOz (42 9 soln.) 8.5 9.1 9.3 9 . 4 10.3 10.3 10.3 10.3 NazO :2:4SiOz (46:9@ s o h ) 8.5 9.1 9.3 9 . 6 10.2 10.3 10.3 10.3 should be remembered that the presence of Sa20 .2.0 Si02 (54.0% s o h ) 8.5 9.1 9.5 9 . 7 10.3 10.3 10.4 10.5 NazO,. 1.6Si0z (62.9% s o h ) 8.4 9.3 9 . 9 10.2 10.5 10.9 10.9 11.2 silicate or phosphate in the water before the 8.5 9 . 5 10.5 10.5 11.0 11.3 1 1 . 3 11.3 NazSiOj.5HzO addition of soap tends to prevent the formaNaaHSiOc5HzO 8.3 10.8 10.9 11 3 11 7 11 9 12 0 NaOH 8.4 10:3 10.9 1 1 . 1 1117 1119 1212 1215 tion of the hard lime-soap curds which are NazBa07.10HzO 8.5 8.7 8.9 8.9 9.0 9.0 9.1 9.1 NalCOs 8 . 5 10.0 1 0 . 1 10.2 10.5 10.5 10.6 especially troublesome when formed on texNaaPO4.12HzO 8.5 9.5 9.9 10.1 10.3 10.5 10.7 l6:9 tiles. Once formed, these curds are difficult Na4PzO7 8.7 9.0 9.3 9.4 9.6 9.8 9.9 10.1 NaeP101s 8 8 8 .. 5 9 8 .. 5 5 8 .. 55 1 8.0 8.1 to remove and most of the solutions used NaaPaO1a 8 .. 5 8 8 8 88 .. 3 8.1 8.1 88.1 .1 here would not be effective for such a purpose. Subject always to the limitations imposed bv the conditions under which this work was cirried out, several conclusions are justified than pure soap alone for producing suds under the conditions on the basisof the results obtained: of this work. In this respect many of the alkalies qualify 1. All of the alkalies studied, with the exce tion of borax, with sodium oleate at 20' C., while a t 60' C.with the sodium showed some ability t o decrease the amount oPsodium oleate stearate only the caustic soda and the crystalline silicates or'sodium stearate required t o form permanent suds in hard water. qualify. 2. The silicates increased in value with decreasing Si0z:NQO ratio. Experience has indicated that the alkali concentration 3. The crystalline silicates (metasilicate and sesquisilicate) range of most practical importance in many washing procwere about as effective with sodium stearate at 60" C. as with esses i s 0.10 per cent or less. Although it cannot safely sodium oleate at 20' C.; all the other alkalies were less so. 4. Both the silicates and phosphates may be employed to be assumed, without trial, that similar results could be obprevent formation of hard lime-soap curds. Caustic soda and tained under greatly changed conditions, the effectiveness of soda ash are not satisfactory in this respect. the metasilicate and the sesquisilicate in this concentration range as compared to that of the more costly pyro- and polyAcknowledgment phosphates should be of special interest to laundries. The author is indebted to C. H. Dedrick who carried out the laboratory measurements for the investigation, to Comparison of Sulfates and Chlorides C. L. Baker who directed the project, and to William Stericker for valued criticism in preparing this report. The effect of the sulfates as compared to the chlorides in the synthetic hard water is indicated by the curves in Figure 5. Literature Cited Both the metasilicate and pyrophosphate required somewhat (1) Am. Pub. Health Assoc., StandadMethods of Water Ansly&, more soap in this water than they did under exactly the same 8th ed., p. 61 (1935). conditions in water containing chlorides. However, the re(2) Carter, J. D.,IND. ENGI. CHEM.,23,1389 (1931). (3) Carter, 3. D., and Stericker, W., Ibid., 26, 277 (1934). lation between the two alkalies remained unchanged; i. e., the ( 4 ) Cobbs, W. W., Harris, J. C.,and Eck, J. R., Oil & Soap, 17, two materials gave similar results over the lower concentration No. 1 , B (1940). range, but the phosphate appeared t o have some definite ad(6) Stericker, W., IND. ENQ. CHIM.,15,244(1923). vantage as the amount used was increased. No completely satisfactory explanation can be offered a t this time for the higher soap consumption in sulfate water than Correction in that containing chlorides. The measurements made in I n the editorial entitled "Alcohol and Our War" [IND. ENO. this phase of the work were limited in number but were suffiCHEM., 34, 511 (1942)J an inaccurate statement was made cient to indicate the comparative efficiency of the two alkaregarding the per capita consumption of sugar in England and lies under these conditions. I n this connection there is reason the United States. American consumption of sugar is normally to believe that other changes in the type of hardness in the somewhat over 100 pounds per capita per annum, which is about water would be reflected in the soap requirements for permaequal to British consumption over the five years preceding the nent suds. Hard waters containing calcium alone, magneoutbreak of the present war. This is four times the British sium alone, or proportions of the two differing from those wartime consumption of sugar and not four times the British used here might respond in a somewhat different fashion to normal as stated in the editorial. the alkaline treatment. TURE
(20-25" C.)
.
