CN1070470C - Method for purification of 2-hydroxynaphthalene -6 -carboxylic acid - Google Patents
Method for purification of 2-hydroxynaphthalene -6 -carboxylic acid Download PDFInfo
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- CN1070470C CN1070470C CN97122794A CN97122794A CN1070470C CN 1070470 C CN1070470 C CN 1070470C CN 97122794 A CN97122794 A CN 97122794A CN 97122794 A CN97122794 A CN 97122794A CN 1070470 C CN1070470 C CN 1070470C
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Abstract
To simply purify a crude product of the subject compound into a high-purity product low in metal ion content by dissolving crude 2- hydroxynaphthalene-6-carboxylic acid in a water-soluble medium by an alkali substance and precipitating with an acid at a pH value in a specific range. (A) Crude 2-hydroxynaphthalene-6-carboxylic acid is dissolved in (B) a water solvent, for example, water of 2-100 times as much as the component A, by using (C) an alkali substance such as an alkali metal hydroxide, ammonia or a lower aliphatic amine in an amount of 0.8-2.0mol% based on the component A and optionally adding (D) 1-10mol% of an antioxidant based on the component A, and then is precipitated with an acid by adjusting to pH 2.0-5.0 with the acid such as hydrochloric acid, sulfuric acid, formic acid, acetic acid or propionic acid.
Description
The invention relates to the method for refining of 2 hydroxy naphthalene-6-carboxylic acid (hereinafter to be referred as " 2.6 acid ").More detailed saying is the process for purification about 2.6 acid of following feature.That is, rough 2.6 acid in water solvent, are added oxidation inhibitor as required, after the dissolving of use alkaline matter, carry out activated carbon treatment as required, adjusting the pH value is 2～5, separates out 2.6 acid.
2.6 acid is very important compound as electronic material macromolecular compound monomer etc.As of monomer used 2.6 acid of this electronic material, not only require organic composition purity height, and, require the containing ratio of metal ions such as low Na, K, Fe for avoiding metal ion to the electronic material Effect on Performance with polymkeric substance.
About the manufacture method of 2.6 acid, disclosed as in No. 1593816 communiques of United States Patent (USP), day clear 57-95939 communique of the disclosure etc., having, generally be to utilize the sylvite of 2 hydroxy naphthalene and the method that carbonic acid gas carries out the Kolbe-Schmit reaction.Yet rough 2.6 acid that obtain like this contain raw material, isomer, tarry matters, tint permanence material etc., so the essential purity that improves.
For such problem, process for purification to rough 2.6 acid has various motions, for example, Japan's special permission is openly put down into the 1-216955 communique and is openly equalled into disclosed method in the 2-218634 communique with Japanese special permission, with rough 2.6 acid (total impurities 0.73%), carry out recrystallization by ether solvents such as water miscibility chain or annular aliphatic ether, aliphatic polyether or aliphatic hydroxyl ethers, obtain the product of high purity (total impurities is lower than 0.2%), but its refining yield is lower than 72%, and difficult solvent recovery, be unfavorable for industrial production.
In addition, in these communiques,, not clear and definite for metal ion containing ratio in 2.6 acid after refining about not record of metal ion yet.
Present inventors just make has highly purified 2.6 acid of hoping, the process for purification that reaches it has carried out conscientiously research, found that to obtain the purity height, and the short-cut method of few 2.6 acid of metal ion content, and finished the present invention.That is, the purpose of this invention is to provide a kind of industrial production that is suitable for, can obtain the process for purification of highly purified 2.6 acid.
For the main idea of the present invention that solves above-mentioned problem as follows:
1. with rough 2.6 acid, in water solvent, after the alkaline matter dissolving, adjusting the pH value is 2.0～5.0, and 2.6 acid outs are gone out, as the process for purification of 2.6 acid of feature.
2. for the above-mentioned 1. method of record,, use the water of 2-100 times of weight for rough 2.6 acid.
3. for method 1. above-mentioned or that 2. put down in writing,, can from alkali metal hydroxide, ammonia and lower aliphatic amine, choose the alkaline matters that use 0.8～2.0 times of mole more than 1 to 2 kind, for rough 2.6 acid as alkaline matter.
4. for state 1., the 2. or 3. method of record, when rough 2.6 acid are dissolved with alkaline matter, for the oxidation inhibitors of 1～20 mole of % of rough 2.6 acid uses.
5. 1. above-mentioned～4. in the method for each record, can from hydrochloric acid, sulfuric acid, formic acid, acetic acid and propionic acid, select more than 1～2 kind with acid as pH regulator.
The present invention is made of above-mentioned steps, the elementary operation of process for purification of the present invention be with 2.6 acid in water solvent, with after the alkaline matter dissolving, the pH value is adjusted to 2.0～5.0, separate out 2.6 acid.
As rough 2.6 acid of using among the present invention, the thick resultant that for example has the Kolbe-Schmit reaction of the sylvite that utilizes 2 hydroxy naphthalene and carbon dioxide to make utilizes this method to modulate but not only be defined in.In rough 2.6 acid that utilize aforesaid method to make, sneak into raw material, isomer, decomposition product etc., for example inevitably, contain raw material 2 hydroxy naphthalene, 2 hydroxy naphthalene-3-carboxylic acid, 2 hydroxy naphthalene-3, isomer such as 6-dicarboxylic acid, metal ions such as Na, K, Fe; Be coloured to and grade.
The inventive method at first, in water solvent, is dissolved above-mentioned 2.6 rough acid with alkaline matter.
The amount of used water solvent for rough 2.6 acid, is used 2-100 times of weight, best 5～50 times of weight.During for 2 times of weight of usefulness quantity not sufficient of the water of rough 2.6 acid, rough 2.6 acid are difficult to abundant dissolving, and when surpassing 100 times of weight, utilize when regulating pH and separating out 2.6 acid, have the danger of a large amount of losses of 2.6 acid, have increased the wastewater treatment expense.Institute's water uses Purified Water (for example, ion exchanged water, distilled water etc.) better.
As alkaline matter, be to make 2.6 acid dissolved alkaline matter in water, this there is not particular determination, for example can use lower aliphatic amine such as alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, triethylamine, trolamine, ammoniacal liquor (and/or ammonia) etc., operating especially, letter makes, and, just reduce metal ion content and set out, preferably use ammoniacal liquor and/or ammonia.Above-mentioned in addition alkaline matter can more than 2 kinds and be used.
For rough 2.6 acid, the consumption of alkaline matter preferably can for rough 2.6 acid, generally use 0.8～2.0 times of mole, the alkaline matter of best 0.9～1.3 times of mole with rough 2.6 acid dissolved amount in solvent.For rough 2.6 acid, during 0.8 times of mole of the usefulness quantity not sufficient of alkaline matter, 2.6 acid can not be dissolved fully, when surpassing 2.0 times of moles, have increased economical load again.
Temperature for thick 2.6 acid of dissolving does not have particular determination, can carry out in the optimal temperature scope below the solvent boiling point in room temperature, but generally carry out under heating for the solubleness that improves rough 2.6 acid, 50～95 ℃, is preferably between 65-90 ℃.
When above-mentioned rough 2.6 acid are dissolved,, can add oxidation inhibitor as required for preventing 2.6 acid oxidases.As oxidation inhibitor, sodium sulfhydrate, formaldehyde sodium hydrosulfite, acid accumulator sulfite etc. are for example arranged.Though the consumption to oxidation inhibitor does not have particular determination, usually 1～20 mole of % is used in rough 2.6 acid.
Have, for preventing the oxidation of 2.6 acid, dissolving operates in to be carried out under the rare gas element (for example, nitrogen, argon gas etc.) better again.
So the alkaline aqueous solution of rough 2.6 acid that obtain can carry out the activated carbon treatment decolouring as required.
At the above-mentioned synthetic rough 2.6 acid-basicity aqueous solution, then interpolation acid, adjust pH are 2.0-5.0, by 2.6 acid that collection is separated out, obtain rough 2.6 acid.
As acid, can use various acid, for example, organic acids such as inorganic acids such as hydrochloric acid, sulfuric acid, formic acid, acetic acid, propionic acid, methylsulfonic acid are arranged.Best, the acetic acid of the imitative family of soluble rudimentary fat carboxylic acid in the water, formic acid, propionic acid are better.Also can inorganic acids and organic acid and usefulness.
In this process, the pH value is adjusted to 2.0～5.0, between best 3.6～4.8.The pH value is lower than at 2.0 o'clock, and the danger of sneaking into isomer is arranged, and is higher than at 5.0 o'clock, and the danger that reduces rough yield is arranged.
In the alkaline aqueous solution of rough 2.6 acid, add acid, can under suitable temperature, carry out, as previously mentioned, because rough 2.6 acid are ideal in the dissolving down of heating, so interpolation acid in the solution of warm-up mode (50-95 ℃, preferably 65-90 ℃), separate out 2.6 acid, then, reduce the temperature to room temperature～0 ℃, finish crystallization and separate out.The crystallization of separating out, method adopts means such as filtration, centrifugation to separate routinely, as required, with less water washing, drying, obtains rough 2.6 acid.
Below, the order of process for purification is elaborated according to the present invention, is 2-100 times of weight for rough 2.6 acid, preferably in the water of 5-50 times of weight, add rough 2.6 acid, in room temperature or improve under the temperature (boiling point below), adding is selected from the alkaline matter more than a kind or 2 kinds in the lower aliphatic amine such as sodium hydroxide, potassium hydroxide, ammonia and triethylamine etc., for rough 2.6 acid, add-on is 0.8～2.0 times of mole, and best 0.9～1.3 times of mole dissolves rough 2.6 acid.Processing is carried out more favourable under rare gas element, is preferably under the nitrogen.
During dissolving, if desired,, can use the oxidation inhibitor more than a kind or 2 kinds in the sodium sulfhydrate, formaldehyde sodium hydrosulfite, acid accumulator sulfite etc. of 1-20 mole % for rough 2.6 acid.After the dissolving, if desired, can carry out activated carbon treatment.
And then, if need, in this stage, add salt such as sodium oxide, Repone K, ammonium chloride, vitriolate of tartar, sodium sulfate, ammonium sulfate, do not have and saltout to 30 (weight) % saltout (Salting out), best saltouing of 5-15 (weight) % separated with the basic salt of 2.6 acid, and be refining, then, the salt of saltouing again after the dissolving, is utilized the acid that adds described later in water, separate out.According to this method, the purity of rough 2.6 acid is improved more.In addition, the salt that uses in saltouing preferably and the alkali kinds of 2.6 hydrochlorates for a kind of salt.
Go out 2.6 acid by adding acid out, preferably carry out under the following conditions.50-95 ℃, preferably in 65-90 ℃ the temperature range, the pH value is 2.0-5.0, preferably in the scope of 3.6-4.8.As acid, organic acids such as mineral acids such as hydrochloric acid, sulfuric acid, formic acid, acetic acid, propionic acid, methylsulfonic acid are arranged.Good especially is soluble lower aliphatic carboxylic acid in the water.
After pH adjusts, finish crystallization in the temperature of room temperature to 0 ℃ usually and separate out, 2.6 acid crystals of separating out for example, utilize means such as filtration to isolate solvent, wash as required, drying.
Process for purification of the present invention not only is defined in above-mentioned explanation, also can suitably change form of implementation.For example, in dissolution process in the synthetic thick 2.6 acid-basicity solution, can after adding precipitation aid such as cellulose powder, filter, also can pay to add and remove tarry matters, be mingled with operation such as material.
The great advantage of the inventive method is the purity height of 2.6 acid of acquisition, refining can in water solvent, carrying out, thus not only help removing metal ion etc., and, just do not pollute global environment because of not with an organic solvent yet.
Embodiment
Followingly illustrate in greater detail the present invention, but the present invention is not limited in these embodiment according to embodiment.
In following examples, get three kinds of rough 2.6 acid as raw material, these raw materials mainly contain following foreign material.
1. rough 2.6 acid of raw material No.1 (purity: the impurity 88.1 (weight) %)
2 hydroxy naphthalene-3-carboxylic acid 8.30 (weight %)
2 hydroxy naphthalene-3,6-dicarboxylic acid 0.67 (weight %)
2 hydroxy naphthalene 0.31 (weight %)
Na 87ppm
K 417ppm
Fe 6ppm
2. the rough 2.6 acid (purity: the foreign material 92.0%) of raw material No.2
2 hydroxy naphthalene-3-carboxylic acid 2.66 (weight %)
2 hydroxy naphthalene-3,6-dicarboxylic acid 0.70 (weight %)
2 hydroxy naphthalene 0.48 (weight %)
Na 70ppm
K 315ppm
Fe 15ppm
3. the rough 2.6 acid (purity: the impurity 88.1%) of raw material No.3
2 hydroxy naphthalene-3-carboxylic acid 0.38 (weight %)
2 hydroxy naphthalene-3,6-dicarboxylic acid 1.62 (weight %)
2 hydroxy naphthalene 0.20 (weight %)
Na 75ppm
K 320ppm
Fe 4ppm
Embodiment 1
Under nitrogen gas stream, with rough 2.6 acid of 11.3g raw material No.1 (purity 88.1 (weight) %) and 0.9g 65% ammonium sulphite, join in the 150ml water, be heated to 70 ℃ after, add the sodium hydroxide of 8.2g 30% again, dissolve.The pH of this moment is 8.0.This solution is warmed up to 90 ℃, and to keep this temperature, the hydrochloric acid of Dropwise 35 % to make pH be 3.6.Subsequently, cool to room temperature, 2.6 acid crystals that leaching is separated out from this solution with 50ml ion-exchange water washing, drying, obtain refining 2.6 acid of 9.5g, and purity is 97.7%, and refining yield is 92.9%.
Embodiment 2
30% sodium hydroxide in using the aqueous ammonia to replace embodiment 1 of 3.9g 28%, other enforcement is identical with embodiment 1, obtains refining 2.6 acid of 9.4g, and purity is 99.1%, and refining yield is 93.2%.
Embodiment 3
Except replace 35% hydrochloric acid among the embodiment 2 with 8.0g acetic acid, other enforcement is identical with embodiment 2, obtains refining 2.6 acid of 9.0g.Purity is 99.3%, and refining yield is 90.5%.Impurity in refining 2.6 acid of gained is as follows.
2 hydroxy naphthalene-3-carboxylic 0.21 (weight %)
2 hydroxy naphthalene-3,6-dicarboxylic acid 0.29 (weight %)
Below the 2 hydroxy naphthalene 0.05 (weight %)
Na 1ppm
K 1ppm
Fe 2ppm
Embodiment 4
35% hydrochloric acid in the formic acid replacement embodiment 2 that uses 4.4g 88%, other is implemented according to embodiment 2, obtains refining 2.6 acid of 9.6g.Purity is 97.6%, and refining yield is 93.8%.
Embodiment 5
Under nitrogen gas stream, (purity 92.0 (weight) %) joins in the 100ml water with rough 2.6 acid of 15.0g raw material No.2, be heated to 70 ℃ after, add the ammoniacal liquor of 5.3g 28% again, dissolving.The pH of this moment is 7.0, and this solution is warmed up to 90 ℃, and it is 4.8 that dropping acetic acid makes pH.Behind the cool to room temperature, 2.6 acid crystals that leaching is separated out from this solution with the washing of 67ml tap water, carry out drying, obtain refining 2.6 acid of 13.2g.Purity is 99.7%, refining yield 95.4%.Impurity is as follows in refining 2.6 acid of gained.
2 hydroxy naphthalene-below the 3-carboxylic acid 0.05 (weight %)
2 hydroxy naphthalene-3,6-dicarboxylic acid 0.28 (weight %)
Below the 2 hydroxy naphthalene 0.05 (weight %)
Na 7ppm
K 2ppm
Fe 5ppm
Embodiment 6
Under nitrogen gas stream, (purity 88.1 (weight) %) joins in the 300ml water with rough 2.6 acid of 22.5g raw material No.3, be heated to 70 ℃ after, with the ammonia solvent of 7.1g 28%.The pH of this moment is 7.0.This solution is warmed up to 90 ℃, and dripping acetic acid again is 4.8 to pH.Behind the cool to room temperature, 2.6 acid crystals that leaching is separated out from this solution with the washing of 100ml tap water, are done quick-friedly, obtain 18.4g and make with extra care 2.6 acid, and purity is 99.4%, and refining yield is 91.3%.Impurity in refining 2.6 acid of gained is as follows.
2 hydroxy naphthalene-3-carboxylic acid 0.05 (weight) is below the %
2-hydroxyl-3,6-dicarboxylic acid 0.56 (weight) %
2 hydroxy naphthalene 0.04 (weight) %
Na 9ppm
K 4ppm
Fe 1ppm
Embodiment 7
Under nitrogen gas stream, rough 2.6 acid of 22.5g raw material No.3 (purity 88.1 (weight) %) and the ammonium sulphite of 1.7g 65% are joined in the 150ml water, after being heated to 70 ℃, use the ammonia solvent of 7.8g 28% again, add 19.5g ammonium chloride and saltout, be cooled to 15 ℃ after, the 2.6 acid ammonium salt crystallizations that leaching is separated out from this solution, use the ammonium chloride water washing of 50ml 5 (weight) % again, in this 2.6 acid ammonium salt stage, the purity of 2.6 acid is 99.9%.
Equally, this 2.6 acid ammonium salt is dissolved in the water, the same with embodiment 6, adjust the pH value with acetic acid, obtain highly purified refining 2.6 acid.
Comparative example
Carry out the special permission of above-mentioned Japan and openly put down into example 10 tests of putting down in writing in the 1-216955 communique.That is, under nitrogen gas stream, (purity 88.1 (weight) %) joins 96ml 1 with rough 2.6 acid of 25gNo.3 raw material, in the mixed solution of 4-diox and 24ml water, is heated to 70 ℃, dissolving.After the 1g activated carbon treatment, cooling, 2.6 acid crystals that leaching is separated out from this solution with the washing with alcohol of 25 (volume) %, drying, get refining 2.6 acid of 11.1g.Purity is 98.6%, and refining yield is 55.1%.With such comparative example method, refining yield is very low, and, reclaim because solvent is essential, be unfavorable for very much industrial production.Impurity in refining 2.6 acid of gained is as follows.
2 hydroxy naphthalene-3-carboxylic acid 0.02 (weight %)
2 hydroxy naphthalene-3,6-dicarboxylic acid 0.32 (weight %)
2 hydroxy naphthalene 0.04 (weight %)
As above, according to process for purification of the present invention, can obtain highly purified 2.6 acid of high yield.And this process for purification is easy.Particularly not with an organic solvent, and in water solvent, carry out, also just there is no need to reclaim solvent,, simultaneously, also obtained to reduce the effect of metal ion contents such as Na, K, Fe so refining expense reduces.
Claims (5)
1, the process for purification of a kind of 2 hydroxy naphthalene-6-carboxylic acid, it is characterized in that with rough 2 hydroxy naphthalene-6-carboxylic acid in water solvent with after the alkaline matter dissolving, adjustment pH is 2.0-5.0, separates out 2 hydroxy naphthalene-6-carboxylic acid.
2, according to the method for claim 1 record, it is characterized in that, use the water of 2-100 times of weight rough 2-hydroxyl-6-carboxylic acid.
3, method according to claim 1 and 2 is characterized in that, as alkaline matter, can use to be selected from alkali metal hydroxide, in ammonia and the lower aliphatic amine more than a kind or 2 kinds, for rough 2 hydroxy naphthalene-6-carboxylic acid, use doubly mole of 0.8-2.0.
4, method according to claim 1 and 2 is characterized in that, when alkaline matter dissolves rough 2 hydroxy naphthalene-6-hydroxy acid, rough 2-hydroxyl-6-carboxylic is added the oxidation inhibitor of 1-20 mole %.
5, method according to claim 1 and 2 is characterized in that, as the acid of regulating pH, and 1 in available hydrochloric acid, sulfuric acid, formic acid, acetic acid and the propionic acid or more than 2 kind.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP297136/1996 | 1996-10-18 | ||
| JP297136/96 | 1996-10-18 | ||
| JP29713696A JPH10120624A (en) | 1996-10-18 | 1996-10-18 | Purification of 2-hydroxymephthalene-6-carboxylic acid |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1181371A CN1181371A (en) | 1998-05-13 |
| CN1070470C true CN1070470C (en) | 2001-09-05 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN97122794A Expired - Fee Related CN1070470C (en) | 1996-10-18 | 1997-10-18 | Method for purification of 2-hydroxynaphthalene -6 -carboxylic acid |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH10120624A (en) |
| CN (1) | CN1070470C (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TW527451B (en) * | 1999-08-24 | 2003-04-11 | Ueno Seiyaku Oyo Kenkyujo Kk | Columnar crystals of 6-hydroxy-2-naphthoic acid and process for manufacturing the same |
| JP4507486B2 (en) * | 2002-09-02 | 2010-07-21 | エア・ウォーター株式会社 | Purification method of carboxylic acid |
| JP5236275B2 (en) * | 2007-12-25 | 2013-07-17 | 上野製薬株式会社 | Method for recovering 6-hydroxy-2-naphthoic acid |
| JP5236274B2 (en) * | 2007-12-25 | 2013-07-17 | 上野製薬株式会社 | Method for producing 6-hydroxy-2-naphthoic acid regenerated product |
| CN102173988B (en) * | 2011-03-25 | 2013-05-01 | 衢州英特高分子材料有限公司 | Purification method of 6-hydroxyl-2-naphthoic acid |
| CN103360242A (en) * | 2012-04-09 | 2013-10-23 | 盐城拜克化学工业有限公司 | Preparation method of 6-hydroxy-2-naphthoic acid |
| CN113880709A (en) * | 2021-11-15 | 2022-01-04 | 宁夏清研高分子新材料有限公司 | Preparation method of high-purity 2-hydroxy-6-naphthoic acid |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0325925A1 (en) * | 1988-01-15 | 1989-08-02 | Hoechst Aktiengesellschaft | Method for the purification of 2-hydroxy-naphthalene-6-carboxylic acid |
| WO1997018182A1 (en) * | 1995-11-13 | 1997-05-22 | Kabushiki Kaisha Ueno Seiyaku Oyo Kenkyujo | Method for separating and purifying hydroxynaphthalenecarboxylic acids |
-
1996
- 1996-10-18 JP JP29713696A patent/JPH10120624A/en active Pending
-
1997
- 1997-10-18 CN CN97122794A patent/CN1070470C/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0325925A1 (en) * | 1988-01-15 | 1989-08-02 | Hoechst Aktiengesellschaft | Method for the purification of 2-hydroxy-naphthalene-6-carboxylic acid |
| WO1997018182A1 (en) * | 1995-11-13 | 1997-05-22 | Kabushiki Kaisha Ueno Seiyaku Oyo Kenkyujo | Method for separating and purifying hydroxynaphthalenecarboxylic acids |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1181371A (en) | 1998-05-13 |
| JPH10120624A (en) | 1998-05-12 |
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Correction item: Description Correct: Sulfuric acid, formic acid False: Formic acid Number: 19 Page: P2 page P7 line Volume: 14 Correction item: Description Correct: Drop 35% hydrochloric acid False: Drop 5% hydrochloric acid Number: 19 Page: P5 page P11 line Volume: 14 Correction item: Description Correct: 0.05 (wt%) below False: 0.05 (wt%) Number: 19 Page: P5 page P22 line Volume: 14 Correction item: Description Correct: 0.05 (wt%) below False: 0.05 (wt%) Number: 19 Page: P6 page P19 line Volume: 14 Correction item: Description Correct: 0.05 (wt%) below False: 0.05 (wt%) Number: 19 Page: P6 page P7 line Volume: 14 Correction item: Description Correct: 0.05 (wt%) below False: 0.05 (wt%) Number: 19 Page: P6 page P9 line Volume: 14 |
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Free format text: CORRECT: DESCRIPTION Free format text: CORRECT: DESCRIPTION; FROM: 0.05(WEIGHT %) TO: 0.05(WEIGHT % )LOWER Free format text: CORRECT: DESCRIPTION; FROM: SULFATE FORMIC ACID TO: SULFATE, FORMIC ACID Free format text: CORRECT: DESCRIPTION; FROM: DROPWISE 5 % HYDROCHLORIDE TO: DROPWISE 35 % HYDROCHLORIDE |
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