US2229123A - Unhairing hides and skins - Google Patents

Description

Patente Jan. 21, 194i STATES PATENT OFFICE nnnsmme HIDES AND sxms Juliuslfannmuller, North Plainfield, N. J., and 'Hans Schleich, New Dorp, Staten Island, N. Y., assignors to 'Wallerstein Company, Inc., New York, N. Y., a corporation of New York No Drawing. A plication May 2, 1939, Serial No. 271,322

1 1 Claims. (01. 149-2) in order to loosen the hair to such an extent that.

it can be readily removed mechanically, whether by hand or machine.

One objection to this old process has always been that it was too slow. To meet this objection, it has been customary to add to the lime bath so-called sharpening agents such as sodium sulphide, the form of arsenic known as red arsenic and various amines, such as methylamine. While such sharpening agents speed up the loosening of the hair, their use is attended with disadvantages of their own. For example, it has been found that most of such sharpeners can be used only in limited amounts because too large amounts result in damage to the skins or hides.

In fact, even with weak sulphide solutions there is danger of such injury if the bath treatment is prolonged. Moreover, the use of most of these Sharpeners often if not usually, results in damage to or destruction of the hair. This latter point is of considerable importance because the hair, if it can be reclaimed, is or may be a valuable by-product.

As a solution to the dilemma above outlined,

present applicant Julius Pfannmuller has disclosed in a copending application, Serial No.

87,328, a method of treating skins and hides which comprises adding to the lime or other alkaline bath reducing sulphur-oxygen compounds, of which sodium hydrosulphite is an ex- ,7 ample. With such a hath, not only is the hairloosening operation accelerated, as compared to the old lime bath treatment, but there is no dc to the hide or to the hair. Thus, notonly is time saved, but the leather, following hating, tanning and other subsequent operations,

is of superior quality and the hair. can be reclaimed as a by-product.

The sulphur-oxygen compounds in question,

and which are hereinafter considered in more detail, are referred to as "accelerators" for 'con-' venience and to distinguish them from the socalled sharpeners above referred to.

In addition to the coarse long hair, which may' be termed the top hair, skins and hides have visible to the eye. If not eliminated, however, such fine hair shows clearly in the leather as soon as the. skins are finished. As a result, such leather must be graded lower and, though salable, it cannot bring the price of higher grade leathers. 6 The price diiference between two grades of leather is usually large and there may be a differential between the lowwt grade and the highest grade, in the same kinds of skins, of several hundred perccent. 10

The fine hair can be eliminated by the use oi sulphides, such as sodium sulphide, which burns off the hair and this procedure is followed in a number of tanneries. But this burning off involves loss of the top hair which, as above stated, 15 may be a valuable by-product if it can be reclaimed, and also involves danger of damage to the skins.

In tanneries where the 'hair is not eliminated by burning ed, the fine hair is usually removed 20 to a greater or less extent as an incident to the, operations known as scudding" and .slating, subsequent to main dehairing. But such removal often causes considerable difllculty and often results in leather requiring low grading. 25 For example, if the hair is not properly loosened, the. operator has to press down so much on the skin he is apt to scufl or mechanically damage the same, e. g. by chipping out small areas on the grain. A piece of leather may be perfect except 30 for scuffed or' chipped spots or spots of unremoved hairs. But it has to be low graded because it haspoor cutting value and shoemakers, for example, will accept as top grade only those skins which have good cutting value. That 15,-35

skins which have bad spots will involve a certain loss in cutting because such spots may prevent use of considerable areas. a

This problem of hair removal is of relatively little importance if the removal is by hand, as in 0 that case the operator can give each skin a careful and more or less individual treatment. But such hand operations are too costly for the majority' of tannery productions. With hair removal by machinery, it is dimcult to obtain com- 45 plate removal ofv the fine hair, and particularlya uniform removal, without sending or damaging the grain of the skin, v As pointed o t in the eo-pending application above mentioned, when both an accelerator, such 50 as sodium hydrosulphlte, and a sharpener, such as sodium sulphide or red arsenic are added to the bath, the action of the sharpener is greatly enhanced. It follows that when such agents are conjointly used, the requisite period for thorough quently reduced. Such a treatment also loosens the fine hair to such an' extent that its proper removal involves no great difliculty. Such accelerators, however, do not afford any substantial protection to the hair from the attack of the sharpeners and there is, therefore, danger of damage to the hair. It has been found, for example, that when sodium sulphide ((66% Na s) in amounts above 0.1 percent, based on the soaked weight of hides or skins, is used in a lime or other alkaline bath containing an accelerator, such as sodium hydrosulphite, the hair is attacked to a greater or lesser degree.

The difliculty of properly removing fine hair can be materially lessened, at the same time avoiding the danger of damage to the hair and hide and obviating the necessity of expensive hand-beaming or hand-slating operations, by adding to the lime bath caustic alkali or some substance or substances which will generate caustic alkali therein, for example, soda ash. In the co-pending application referred to, there is disclosed the conjoint use of lime, an accelerator, such as sodium hydrosulphite, and caustic'alkali. This solves the probe lem of removal of fine hair to a certain degree.

There is, however, still another problem involved.

If the amount of caustic alkali used is too small, it is still dimcult to remove the fine hair. On the other hand, if the amount of caustic alkali used to obtain desired ease of removing finehair, it

may prove to be too greatan amountin another respect.

properly loosen hair but may so interfere with Su q e t ha ing, an i g or other operations that good grade leather cannot be obtained. i.

Returningto the question of too much caustic, when skins or hides are treated in an alkaline bath r they become swollen and caustic alkali swells out skins and hides much more than lime alone does. Before the skins can be tanned, they must be brought down or reduced." This is accomplished by an operation known as hating or puering. Formerly, puering was applied.to a bath formed from dog manure and hating to a pigeon manure bath or the use of artificial bates containing enzymatic preparations. At present, however, the term "bating" ismore or less commonly used to cover all types of such-procedures. The

hating step is carried out both to render the skins,

leather, the permissible amount of caustic alkali issubjected to close limitations. Thus, the amount of caustic alkali in the lime'bath necessary to 'obtain thorough and proper "action on the fine hair may well bein excess of the limit permissible in respect to the degree of swelling.

It is an object of the present invention to provide a method of treating skins and hides for the loosening of the hair such that the disadvantages involved in the problems above set forth are avoided.

More particularly it is an object of the inven- 5 tion to provide a hair-l treatment such that all the hair, including flne hair, can be removed properly and without undue difilculty and without resort to hand removal and, at the same time, such that there is no substantial damage or injury to hide or hair; such that excessive swelling ofthe skins or hides is avoided; and such that proper leather of good grade can be subsequently obtained.

We have discovered that when hides and'skins are subjected, for example, to the action of lime, sodium sulphide and sodium hydrosulphite under proper conditions and in a particular sequence, a new and unexpected result is obtained as compared to any of the procedures above outlined and 20 more particularly as compared to the action of a bath containing lime, sulphide and hydrosulphitc simultaneously. By such treatment we attain a substantial improvement over the procedures above outlined. 25

In carrying out the invention, and citing the materials specified by way of example, we first subject the hides or skins to the action of a sodium sulphide solution in the absence of lime or other alkaline material. We then subject such hides 30 or'skins to the action of a lime bath containing sodium hydresulphite.

- To this end, we first immerse the hides or skins in an aqueous bath containing sodium sulphide. In tannery practice, it is the usual custom to wash and soak skins and hides prior to any treatmentwith chemicals. The sodium sulphide may be added to the soak water at anytime after a short preliminary wash or the skins or hides may be subjected to the sulphide solution after the soaking 0 operation.

While the time of treatment in the sulphide bath may vary, treatments of from one-half hour to twenty four hours have been found to give satisfactory results. Generally speaking, the shorter the soaking period prior to the sulphide treahnent the longer should the skins or hides remain in the sulphidesolution. However, even with a long soaking, a relatively long sulphide treatment may be used.

The sulphide treatment may be conveniently,

, but not necessarily, carried out in the'paddle ordinarily used in the leather industry, the washed skins being placed therein and the sulphide added to the water. The relative amount of water used 55 may vary but a skin-to-water ratio of about 1 "to .4. based on-soaked or wet salted skin weight,

has been found to give satisfactory results. For

dry skins, considerably more water will ordinarily be required. go

The bath temperature may be in what may be termed the normal range 1. e. from 55 to 70' l".

or somewhat higher. It is considered inadvisable to usetemperaturea above F. In the event clan abnormal drop in room temperature during 05 the process; it may be advisable to adjust the bath temperatures since lower temperatures slow up the process. I

The relative amount of sodium sulphide used may vary. In this connection, we have discovered 70 that the available range depends, at least in part, on the pH value of the sulphide solution and that the range canfbe widened by properly controlling such pH value.

Regardlms 01' pH value, the lean amount. 15

cated do not appear to effect any substantial sodium sulphide that is sufflcient to obtain what are now considered practically effective results, is

about /2 pound concentrated sodium sulphide (66% NazS) per 1000 pounds of skins or hides, figured on soaked weight. An amount between that minimum up to about 5 pounds of such sodium sulphide per 1000 pounds of skins or hides gives satisfactory results and within that range it is normally unnecessary to pay any particular attention to the pH value. If higher proportions are used, the hair is more or less attacked unless the pH value of the bath is properly adjusted. If, for any reason, it is desired to use a higher proportion of sodium sulphide, the danger of damage to the hair can be avoided by adjusting the alkaline reaction of the solution to a pH value below 11.7. We have found that what are now considered the best results are obtained if the pH value is adjusted to around 10.6 or lower.

If adjustment of the pH value is indicated, this may be effected by means of any suitable agentv for reducing the alkalinity. Examples of such agents are sulphuric, muriatic, boric or organic acids; sodium bicarbonate or borate; or other acid salts or salts of a weak base such as ammonium chloride; or organic amines.

If and when the pH value is thus adjusted, the relative amount of sodium sulphide used may be safely increased up to 10 pounds per 1000 pounds of skins or hides. Even a somewhatlarger proportion of sodium sulphide may be used with- V out serious damage to the hair or skins but it is our present belief that with amounts above the maximum mentioned there is no such increase in effectiveness as to warrant such increase in proportions.

After the sulphide treatment above described, I

tries, to designate such salts as hyposulphites.

In view, however, of the fact that the term hyposulphites has long been used in this and other countries to designate salts of thiosulphuric acid (H2S2O3) more properly called thio-sulphates, we prefer to use the term hyposulphites for salts 4 Of the acid H2S204.

Assuming that the skins or hides have been subjected to the sulphide treatment in a paddle, the most convenient procedure is to replace the sulphide liquor with water and then mix in the lime and sodium hydrosulphite. For this bath,

we have found it advisable to have the bath temperature above approximately 60 F., say from 70 to 86 F.

The relative amount of lime used may vary within a considerable range. Ordinarily, amounts between about pounds and 250 pounds per 1000 pounds of skins or hides, based on soaked weight, give satisfactory results but occasionally a somewhat higher proportionis desirable.

The relative amount of sodium hydrosulphite may also vary. We have found that from 4 pounds to -6 pounds per 1000 pounds of skins or hides (soaked weight) gives satisfactory results. Smaller proportions may be used but will be less eifective. Larger proportions may also be used but amounts materially greater than those indichange in the results, and, hence, are unnecessary.

While the duration of treatment in the limehydrosulphite bath may vary, we have found that a treatment of from 2 to 4 days, measured from the time the lime is added, gives satisfactory resuits, the hair, including fine hair, being in such a thoroughly loosened condition as to be readily and properly removable by normal tannery procedure. In this-connection it should be noted that the hair will probably be thoroughly loosened in considerably less than 4 days. As previously suggested, however, the various operations involved .in the production of leather are interrelated. Most tanneries consider that the duration of the lime or other alkaline treatment controls, to a considerable extent, the texture of the final leather. It follows that the duration of I treatment in the lime bath does not depend on the hair loosening factor alone and a longer treatment than required for proper hair loosening may be desirable for other reasons. i I

Skins and hides treated according to the invention as so far described will have an alkaline swelling well below any degree of swelling that is considered excessive in the sense hereinabove referred to. In fact, in many cases, there will not be as much swelling as tanners desire. In such case, the degree of swelling may be increased by, adding to the lime-hydrosulphite bath a caustic alkali. While the amount may vary, we have found that from .05 percent to 5.0 percent, based on soaked or wet salted skin weight gives satisfactory results, the proportion used depending largely on the'degree of swelling desired. That is, the more swelling desired, the greater the proportion of caustic used. In referring to the addition of a caustic alkali, it is to be understood that we include addition of caustic alkali as such or the addition of any compound that will generate caustic alkali in the lime bath, for example, soda ash or sodium sulphite.

Instead of using sodium sulphide in the first bath, other alkaline sulphides may be used.

Instead of using sodium hydrosulphite, other accelerators may be used. For the purposes of the present application, accelerators are to be understood to mean. reducing sulphur-oxygen; combinations, characterized by being relatively stable in the dry state and having a substantially greater reducing power in solution than that of the sulphates, sulphites, sulphides or thio-sulphates. Such combinations include compounds of the class of hydrosulphites and sulphoxylates, e. g. sodium, calcium, magnesium and zinc hydrosulphites and sulphoxylates, and corresponding organic compounds of sulphur and oxygen, such.

as the aldehyde] and ketone derivatives of the hydrosulphites and suiphoxylates. Further examples are sodium, calcium,- or magnesium formaldehyde sulphoxylate; zinc calcium hydrosulphite; sodium, calcium-magnesium or zinc formaldehyde -sulphoxylate or hydrosulphite and other hydrosuiphites and sulphoxylatesof sodium,

I calcium, magnesium and zinc. In short, all sulphinicor disulphinic acid derivatives whether of inorganic or organic origin, aromatic or aliphatic, may be used.

, Instead of lime, or in conjunction with lime, other alkaline materials such, for example, as caustic soda or soda ash, may be used.

With the treatment described, the hair, including fine hair, -is so thoroughly loosened it can readily be removed by normal tannery processes and without the necessity of recourse to removal by hand. At the same time there is no substantial damage or injury to the hair and, thus, the

1 alkaline swelling of the skins or hides.

It has been proposed in a United States patent to treat skins and hides, first in a sulphide solution of an alkalinity represented by a pHof 11.8 to 12.2 and thereafter .to the action of a lime bath. It is stated in such patent that the procedure referred to avoids damage or injury to hide or hair. Whether or not this is true, is a point not here involved. In any event, wehave found that with the procedure proposed in such patent the fine hair is often, if not usually, diflicult to remove. Moreover, we have found that with the pH values prescribed by the patentee as critical and with the proportions of sulphides prescribed by him, the hair is definitely attacked and damaged if, after the sulphide treatment, the skins or hides are subjected to a bath such as we here propose, namely, a. bath containing lime and an accelerator, such as sodium hydrosulphite.

The following more detailed procedures are givenby way of example, such procedures having been found to give satisfactory results.

In each case the hair, including the fine hair, was readily removed. If any fine hair was left after the removal of the main hair, it was removed without difficulty as an incident to scudding. The top hair was of good quality and could be reclaimed as a by-product. The leather, following hating, pickling, tanning, etc. was of excellent quality and good grade.

Where the addition of chemicals is specified,

sufficient agitation to obtain a proper mix is to be understood. Lime means hydrated lime throughout.

The sulphide solution was drained on and re- Example I 1000 pounds calfskins (salted weight) were washed in a drum for about 2 hours and then.

hair fleshed. The skins were then transferred to a paddle containing suflicient water to give a skin-to-water ratio of about 1:4. To this water had been added 3% pounds fused sodium sulphide (66% NazS). The skins were paddled for 30 minutes and allowed to stand in the sulphide bath for After 20 hours, 2.5 pounds soda ash were added and the paddle turned a short time.

After a total of 3 days in the lime bath the skins were removed and unhaired on the usual unhairing machine. a

' Example II 1000 pounds calfskins were soaked overnight and put in a paddle having suflicient water to give a skin-to-water ratio of 1:4.5. Then there was added 4 pounds sodium bicarbonate and, after 10 minutes, 6 pounds sodium sulphide (66% No.18) The skins were kept in this bath for 17 hours. The pH of the soak liquor at end of soaking was placed by water at. 80 F. Then there was added 100 pounds limeand, after 20 minutes, 6 pounds sodium hydrosulphite. After 2 days i the lime 1 bath the skins were unhaired.

exam le 111 1000 pounds goatskins, dry weight, were soaked for one day and put in a paddle containing about 7000 pounds water at about F. Then there was added, in the batches, a total of 8 pounds crystallized sodium sulphide (33% Nags approx.) The skins were paddled for 1% hours. The pH shortly after the first addition was 8.7; after the second addition and at end of paddling, 9.3. The skins were kept in this bath over night.

Next morning the pH of the sulphide liquor was 8.5. The sulphide liquor was drained off and replaced by water at F. There was. then added 300 pounds lime and 3 pounds sodium hydrosulphite. After paddling for one hour and a rest period of 2 hours, there was added 12 pounds soda ash and 7 pounds more sodium hydrosulphite.

After 72 hours the liquor was drained oil. The skins were kept overnight in cold water and then.

, removed and dehaired.

Example IV water to give a skin-to-water ratio of 1:4.5. Then there was added 8 pounds sodium bicarbonate and, after 10 minutes 12 pounds sodium .sulphite (66%NaaS). The skins were left in this bath 3 hours, after which'time the pH was found to be-10.0.

The sulphide solution was replaced by water at 80 F. To this'there was added 200 pounds lime, and, 'after 20 minutes, 12' pounds sodium hydrosulphite. The skins were eft in this bath overnight. Next day there was added 5 pounds soda ash. After a total of 3 days following addition of the lime the skins were removed and unhaired.

Example V 2000 pounds calfskins weresoaked for 16 hours and put in a paddle containing sufllcient water to give a. skin-to-water ratio of 1:4.5. Then there was added 2.5 pounds sodium sulphide (66% N823) The skins were left in this sulphide bath for 4 hours.

The sulphide solution was replaced by water at 78 F. To this wasadded 200zp0unds lime and, after 20 minutes, 12 pounds sodium hydrosulphite; After 24 hours there was added 'lo pounds soda After remaining in the lime bath 3 days the skins were removed and .unhaired.

What is claimed is:

1. The method of loosening the hair of skins and hides which comprises subjecting the-skins or hides to the action of an aqueous bath to which has been added an alkaline sulphide and which is substantially free of any other alkaline material, and thereafter subjecting the skins or hides to the action of an aqueous bath to which has been added an alkaline material and a material selected from the group consisting of hydrosulphites, sulphoxylates and their aldehyde and ketone derivatives.

2. The method of loosening the hair of skins and hides whichcomprises subjecting the skins or hides to the action of an aqueous bathto which has been added an alkaline sulphide and which is substantially free of any other alkaline material, and thereafter subjecting the skins or hides to the action of an aqueous bath to which has been added lime and amaterial selected from the group consisting of hydrosulphites, sulphoxylates and their aldehyde and ketone derivatives.

3. The method of loosening the hair of skins and hides which comprises subjecting the skins or hides to the action of an aqueous bath to which has been added an alkalinesulphide and which is substantially free of any other alkaline material, and thereafter subjecting the skins or hides to the action of an aqueous bath to which has been added an alkaline material and a hydrosulphite.

4. The method of loosening the hair of skins and hides which comprises subjecting the skins or hides to the action of an aqueous bath to which has been added an alkaline sulphide and which is substantially free of any other alkaline material, and thereafter subjecting the skins or hides to the action of an aqueous bath containing lime and a hydrosulphite.

5. The method of loosening the hair of skins and hides which comprises subjecting the sk ns or hides to the action of an aqueous bath to which has been added sodium sulphide and which is substantially free of any other alkaline material, and thereafter subjecting the skins or hides to the action of an aqueous bath containing an alkaline material and sodium hydrosulphite.

6. The method of loosening the hair of skins and hides which comprises subjecting the skins or hides to the action of an aqueous bath to which has been added sodium sulphide and which is substantially free of any other alkaline material, and thereafter subjecting the skins or hides to the action of an aqueous bath containing lime and sodium hydrosulphite.

7. The method of loosening the hair of skins and hides which comprises subjecting the skins or hides to the action of an aqueous bath to which has been added an alkaline sulphide and which is substantially free of any other alkaline material, adjusting the alkaline reaction of the bath to a pH valuebelow 11.7, and thereafter subjecting the skins or hides to the action of an aqueous bath to which has been added an alkaline material and a material selected from the group consisting of hydrosulphites, sulphoxylates and their aldehyde and ketone derivatives.

8. The method of loosening the hair of skins and hides which comprises subjecting the skins or hides to the action of an aqueous bath to which has been added an alkaline sulphide and which is substantially free of any other alkaline material, adjusting the alkaline reaction of the bath to a pH value below 11.7, and thereafter subjecting the skins or hides to the action of an aqueous bath to which has been added lime and a material selected from the group consisting of hydrosulphites, sulphoxylates and their aldehyde and ketone derivatives.

9. The method of loosening the hair of skins and hides which comprises subjecting the skins or hides to the action of an aqueous bath to which has been added sodium sulphide (66% NazS) in an amount between approximately /2 pound and approximately 5 pounds per 1000 pounds of skins or hides, figured on soaked weight, and which is substantially free of other alkaline material, and thereafter subjecting the skins or hides to the action of an aqueous bath to which has been added lime and a material selected from the group consisting of hydrosulphites, sulphoxylates and their aldehyde and ketone derivatives.

10. The method of loosening the hair of skins and hides which comprises subjecting the skins or hides to the action of an aqueous bath to which has been added sodium sulphide (66% 118.28) in an amount between approximately pound and approximately 5 pounds per 1000 pounds of skins or hides, figured on soaked weight, and which is substantially free of other alkaline material, and subjecting the skins or hides to the action of an aqueous bath to which has been added lime and sodium hydrosulphite. 1

11. The method of loosening the hair of skins and hides which comprises-subjecting the skins or hides to the action of an aqueous bath to which has been added sodiumsulphide (66% Nazs) in an amount in excess of approximately 5 pounds per 1000 pounds of skins or hides, fi red on soaked weight, and which is substantially free of other alkaline material, adjusting-the alkaline reaction of the bath to a pH value below 11.7, and thereafter subjecting the-skins or hides to the action of an aqueous bath to which has been added an alkaline material and a material selected from the group consisting of hydrosulphites, suiphoxylates and their aldehyde and ketone derivatives.

12. The method of loosening the hail of skins and hides which comprises subjecting the skins or hides to the action of an aqueous bath to which has been added'scdium-sulphide (66% Na s) in an amount in excess of approximately 5 pounds per 1000 pounds of skins or hides, figured on soaked weight, and which is substantially free of otheralkaline material, adjusting the alkaline reaction of the bath to a pH value below 11.7, and subjecting the skins or hides to the action of an aqueous bath to which has been added lime and sodium hydrosulphite.

13. The method of loosening the hair of skins and hides which comprises subjecting the skinsor hides to the action of an aqueous bath to which has been added an alkaline sulphide and which is substantially free of any other alkaline material, and thereafter subjecting the skins or hides to the action of an aqueous bath to which has been added lime and sodium hydrosulphite, the latter being added in an amount from about 4 pounds to about 6 pounds per 1000 pounds of skins or hides, figured on soaked weight.

14. The method of loosening the hair of skins and hides which comprises subjecting the skins or hides to the action of an aqueous bath to which has been added an alkaline sulphide and which is substantially free of any other alkaline material, and thereafter subjecting the skins or hides to the action of an aqueous bath to which has been added lime and a material selected from the group consisting of hydrosulphites, sulphoxylates' and their aldehyde and ketone derivatives, said second bath also containing a caustic alkali.

15. The method of loosening the hair of skins and hides which comprises soaking the skins or hides in water, adding to the soak water m alkaline sulphide, leaving the skins or hides in such bath for from /2 to 24 hours, replacing said bath with water, adding an alkaline material and a material selected from the group consisting of hydrosulphites, sulphorwlates and their aldehyde and ketone derivatives, and leaving the skins or hides in said second bath for from 2 to 4 days.

16. The method of loosening the hair of skins and hides which comprises subjecting the skins or hides to the action of an aqueous bath, at normal temperature, to which has been added an alkaline sulphide and which is substantially free of other alkaline material, and thereafter subjecting the skins or hides to the action of a warm water bath to which has been added an alkaline material and a material selected from the group consisting of hydrosulphites, sulphoiwlates and their aldehyde and ketone derivatives.

17. The method of loosening the hair of skins and hides which comprises subjecting the skins, or hides to the action of an aqueous bath-to which has been added an alkaline sulphide and which.

5 is substantially free of any other alkaline material, thereafter subjecting the skins or hides to the action of an aqueous bath to which has been added lime and sodium hydrosulphite, and controlling the degreeot swelling of the skins or hides by adding to said second bath suitable amounts of a. caustic alkali.

JULIUS PFANNMULLER. HANS SCHIEICH.

. CERTIFICATE OF CORRECTIOIL I Patent No. 2,229,125. January 21, 191 1.

lTULIUs PFANNHULLER, ET L.

It is herebj certified that error appears in the printed jepecification of the above numbered patent requiring correction as follows: Page 3, first column, line 55,- for "hyposulphits read -"hydrosulphitee"--; and

I that the said Letters .Patent should be read with this correction therein that the same may conform to the record of' the case inthe P atent Office.

Signed and sealed this 18th day of February, A. 1). 19M.

Henry-Van A'rsdale, (Seal) Acting Commissioner ofPatents.