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526
10-Smith, J. IND. END.CHEM., 12, 878 (1920). 11-Downey, “Gelatins,” published by the Edible Gelatine Manufacturers Research Society of America, Inc., 1457 Broadway, New York, N. Y . 12-Sommer, Ice Cream Trade J . , 28, 47 (1927).
VOl. 20, No. 5
13-Leighton and Williams, J . Phys. Chcm., 31, 596 (1927). 14-Dahlberg, N . Y.Agr. E x p . Sla., BUZZ.688 (1926). 15-Leighton, J . Dairy Sci., 10, 300 (1927). l&Moran, Proc. Roy. SOC.(London), A118,30 (1926).
Waste in the Mexican Soap Industry’ G. G. Colin CENTRAL CHEMICAL LABORATORY, MEXICO,D. F.
ERY few of the soap manufacturers in this city con-
V
trol their processes chemically; consequently there is considerable avoidable waste. Domestic raw material is bought and sold without specifications. For example, a fat with 60 per cent saponifiable matter may be sold a t the same price as one containing 98 per cent. Tallow is often grossly adulterated and the fraud not discovered until it has caused considerable loss. I n spite of the empirical methods used the soap industry seems to be profitable here. The manufacturers supply chiefly low-grade soaps for laundering purposes. These soaps contain large quantities of rosin and silicate and are strongly alkaline. The destructive action of the caustic soda on linen has not been brought to the attention of the public. Some manufacturers have attempted to recover glycerol from their spent lyes, but lack of modern equipment and the necessary chemical control have been the cause of many failures to utilize the by-products in a profitable manner. This laboratory was asked to observe and try to improve the defective methods, especially those for the production of crude glycerol, in one of the largest soap factories in the city. However, lack of cooperation and conflicting views prevented to a certain degree an increase in glycerol production from 10 per cent to a t least 70 or 80 per cent of the theory, and a modification of storage facilities to avoid the loss of many tons of lyes containing from 6 to 10 per cent NaOH. This valuable by-product overflowed from the small storage tanks into the sewer and the remainder was given away. Soap manufacturers in this country usually advertise the free distribution of these spent lyes, which are used to soak badly soiled clothes. This destructive method of washing is in great favor among professional washerwomen. Naturally the soaking of clothes, frequently several hours, in a solution containing about, 10 per cent of caustic soda is bound to destroy the fiber. Improvement i n Production of Crude Glycerol
A preliminary examination of a sample of the crude glycerol stock kept in storage (about 8 ton@) showed it to be a lowgrade crude, with the following composition: glycerol 60.0, mineral residue 14.0, and other impurities 26.0 per cent. This material was diluted and treated as an ordinary spent lye. Examination of the impurities showed that the product had simply been pumped into the evaporator with little or no previous treatment to remove the bulk of impurities, and even though the material was rather concentrated, about 32’ BB., the glycerol content was too low. The first product after treatment had a much lighter color and showed upon analysis about 78 per cent glycerol. The usual clarification method with alum and lime, after treatment with acid, gave a fairly good crude ranging between 75 and 80 per cent glycerol. Received November 22. 1927. Metric tons are meant when figures are given in tons. but the metric is used in Mexico. 1 f
No system
The question of increasing production came up. The consumption of fats and oils was found to be from 200 to 300 tons per month. Assuming an 8 per cent yield of glycerol it was considered feasible to produce a t least 10 or 12 tons of crude glycerol, allowing a 1 per cent loss for the amount retained in the soap and for that contained in the freely distributed lyes. The work was unduly retarded because lyes containing from 6 to 10 per cent NaOH were sent to the glycerol department. Batches of about 10 tons were given the acid treatment. Lyes containing from 6 to 10 per cent sodium hydroxide require about 750 to 1250 kg. of 66’ BB. sulfuric acid, with a cost of from $93 to $233 (Mexican currency). This expense, added to fuel and labor, brought the cost of production to a prohibitive level. The fact that the soap master was used to the lavish expenditure of caustic soda in his processes made it difficult to have him utilize the “hard” lyes again for saponification; when returned to him the material would be stored away in the small storage tanks and any excess would overflow into the sewer. The total storage capacity of the tanks (even using some destined to the storage of liquid fats) was about 50,000 liters against a monthly production of at least 200,000 to 300,000 liters. Usually the available volume of workable lyes was 10,000 to 20,000 liters, which of course was only a small part of the total volume that could be utilized profitably. The real available volume of soap-spent lyes had never been worked out before, so that no storage facilities were a t hand. When an attempt was made to reduce the alkalinity of some “hard” lyes, at least six extra men had to be hired to convey the resulting soap to the main kettles, to be used as foots. This material had to be carried in buckets, from lack of elevators and direct communication between the glycerol and soapmaking departments. A close competitor to this soap manufacturer was interviewed in order to secure more soap lyes to be worked. This manufacturer could furnish lyes guaranteed to contain not over 0.5 per cent sodium hydroxide and not less than 7 per cent glycerol. This material could not be used again on account of lack of storage facilities and because the purchase of this by-product introduced another expense to be charged to the already high cost of manufacture. The following estimate was made of the possibilities of increasing the production of crude glycerol, provided the necessary facilities were givens: TANK
LYE
Lilers 1 2 3
20,000 10,000 20,000
ALKALINITY Per cent 6.2 4.3 6.0
N-aOH
K4. 1340 430 1200
TOTALA
2970
Deduction of NaOH neutralized from the acid-treatedmaterial for treatment with coagulants: TANK 1 2 3
LYE
ALKALINITY
NaOH
Lilers
Per cent
Kg.
20,000 10,000 20,000
0.50 0.03 0.60
100 30 120 ~
TOTAL B
250
May, 1928
INDUSTRIAL AND ENGINEERING CHEMISTRY
A -B left a net weight of 2720 kg. of NaOH, which with a fair allowance for loss amounted to about $700 in one month only, in that small volume of by-product. The actual loss in 200,000 liters would be $2800, or about $33,600 a year. Utilization of “Hard” Lyes
A few preliminary experiments were carried out in the laboratory to determine the possibility of utilizing those “hard” lyes for saponification by further treatment with fat. However, since facilities to avoid loss of time and unnecessary labor were lacking, this process was not carried out. Some of thb so-called “waste lyes” contained about 10 per cent glycerol and 5 per cent alkalinity. These went partly into the sewer and the rest was given away. In two months the following quantities of fats and rosin were used: KP. Tallow Coconut oil Cottonseed oil Sesame oil Rosin Castor oil Various others TOTAL(without rosin)
i76,-ioi 19,060 185,636 4,861 67,876 5.400 .,-..
850 391,908
Theoretically, basing the calculation on minimum and maximum index of saponification, 391,908 kg. of fat should require not less than 54 nor more than 55.5 tons of caustic soda. The records showed an actual consumption of about 96 tons during those two months. Granting that a large excess should be necessary to carry out the saponification, some measure was imperative to find use for the large volume of “hard” lyes that went to waste. Estimating roughly, in those two months there was loss of about 35 tons, amounting to about $8000 (Mexican currency). At that rate a conservative estimate indicated a yearly loss of not less than Si0,OOO worth of caustic soda. From 391,908 kg. of fat a
527
glycerol yield of 8 per cent, or about 30 tons of crude, could be expected. Lack of a sufficient supply of workable lyes made it impossible to produce more than 6 or 8 tons of crude per month, and often not more than 3 or 4 tons. The glycerol plant was located near the steam boiler, and leaks in the steam pipes created a rather humid atmosphere. Therefore, owing to the hygroscopic nature of glycerol, defects in construction of the storage tanks, and crude operating methods, it was not surprising that the glycerol should show dilution. A change of location of the plant was suggested and proposals were submitted for the purchase of a modern doubleeffect evaporating outfit. It was also suggested that the manufacture of the c. P. product would be a paying investment, if a larger volume of lye were taken by purchasing the by-product from other soap manufacturers. Recovery of Salt
An examination was also made of the salt obtained from the evaporation of the treated lyes. It was suggested that it could be used several times before discarded in the saltingout operation, instead of thrown away as was the custom. Analysis of the material as compared with the new salt gave the following results: NaCl
so4
Moisture Other impurities Solubility
hTEW RECOVERED Per cent Per cent 89 00 70.00 0.73 10.30 4 00 8.70 6.27 11.00 Immediate in both
On the basis of sodium chloride, this recovered material would have a value of about 5 cents per kilogram against 6.5 cents for the new salt.
Thermal Decomposition of Organic Sulfur Compounds‘ *
W. F. Faragher, J,. C. Morrell, and S. Comay UNIVERSAL OIL PROl>UCTS COMPANY, CHICAGO, ILL.
T IS generally known in The object of this investigation was to study the sulfides, and mercaptans, disthe refining industry that thermal decomposition of organic sulfur compounds closed little that was pertinent and to relate the results to the changes which take to the present investigation. crude oil and its distilplace during the refining and cracking of oil. lates containing compounds O t t o a n d Rossing2 state of sulfur produce hydrogen The following organic sulfur compounds were sethat amyl disulfide is gradusulfide upon heating-as, for lected as representative of these types which are conally decomposed when disexample, during distillation. sidered to be present in petroleum: mercaptans, alkyl tilled a t atmospheric pressure, Eyen distillates t h a t h a v e sulfides, alkyl disulfides, thiophene, and elementary with the splitting off of sulfur sulfur. All these substances were dissolved in naphtha been sweetened prior to reor sulfides richer i n s u l f u r distillation are known to form made from Pennsylvania crude oil. The vaporized than the original substance, mercaptans and hydrogen sulsolutions were subjected to an average temperature of leaving behind a tarry resi496” c. The products of the thermal decomposition due of dark color. Table I fide. The principal cause of were identified. c o r r o si o n in high-pressure summarizes the results obComparative tests were then made with products of stills is hydrogen sulfide. The tained in the present work by Sources of the corroding agent, cracking in the liquid vapor phase under pressure. distillation of the disulfides hydrogen sulfide, have never shown. been identified. A study of the ~hWma1decomposition of Table I-Diatillation of Alkyl Disulfides at Atmospheric Pressure organic sulfur comDounds was therefore undertaken and the DISULFIDE OBSERVATION AND ANALYSIS OF DISTILLATE of H2S or RSH. no loss. very little change in color results were relate‘d to the changes which take place dur- ~ ~ ~ ~ pNN oo ytrace trace l of HzS or RSH; no 10s;; slightly yellow n-Butyl ing the cracking and refining of oil. No trace of HzS, but a trace of RSH: practically no loss HzS in large quantity; aboFt 9% of RSH; loss about 1%; A search of the literature upon the thermal decomposition isoamyl highly colored; tarry residue Of compounds, such as the diThe following organic sulfur compounds were selected 1 Presepted under the tltle “Thermal Decomposition of Sulfur Derepresentative of those types which are considered to be rivatives of Hydrocarbons” before the Division of Petroleum Chemistry present in petroleum: mercaptans, at the 74th Meeting of the American Chemical Society, Detroit, Mich.,
I
September 5 to 10, 1937.
* Bel., 19, 3134 (1886).
