(1) Determination of total lipids
The total fats in the fatty acid soap collector include various hydrocarbon-based hydroxy acids and neutral organic substances such as unsaponifiables in oxidized paraffin soap, neutral oils in alkali slag, and the like. There are two methods for determining total lipids, waxing and solvent extraction.
1. Wax and reagents. Methyl orange indicator 20-30% sulfuric acid; white wax.
operating. Take about 10 grams of fatty acid soap sample, weigh accurately to 0.0001 grams, put it in a 100 ml beaker, add about 50 ml of distilled water to heat and dissolve, add 2-3 drops of methyl orange indicator, then use 20^30% The acidification of sulfuric acid makes the aqueous solution strongly acidic, and is heated and boiled on an electric furnace to make the lower aqueous solution reddish, and the upper layer is a transparent fatty acid layer. A predetermined amount of white wax of known weight is prepared and stirred with a glass rod; it is made miscible with the fatty acid layer. After the wax and the fatty acid are mutually melted, the glass rod is placed in a cold water bath together with the beaker to cool until the fatty acid layer is completely solidified into wax . The wax was taken out with a glass rod, and the water on the wax was carefully blotted dry with a filter paper, and the wax was weighed. The total lipid content can be calculated according to the following formula
Wax weight (g) - white wax weight (g)
Total fat, %=——————————————×100%
Sample weight (g)
2. Solvent extraction method Reagents. Methyl orange indicator; 20-30% ethyl sulphate (for oxidized paraffin soap) or 30-60 ° C petroleum ether (for petroleum alkali slag).
operating. Take about 2 grams of fatty acid soap sample, weigh it to 0.0001g, put it in a 100ml beaker, add about 50ml of distilled water to heat and dissolve, add 2-3 drops of methyl orange indicator, then use 20~30% Acidification of the sulfuric acid causes the aqueous solution to be reddish. The solution was transferred to a separatory funnel while hot, and after standing to separate the layers, the lower aqueous solution was partitioned into another separatory funnel, and the lower aqueous solution was extracted with diethyl ether or petroleum ether until diethyl ether or petroleum ether was colorless. The ether or petroleum ether extract was combined with the fatty acid layer, and diethyl ether or petroleum ether was evaporated on a water bath, and dried at 105 ° C to constant weight. Total fat can be calculated according to the following formula
Extract weight (g)
Total fat%=—————————×100
Sample weight (g)
(2) Determination of the content of unsaponifiable (or neutral oil)
Reagents. Ether (suitable for the determination of unsaponifiables) or 30-600C petroleum ether (suitable for the determination of neutral oils).
operating. Take 2-3 grams of fatty acid soap sample, weighed accurately to 0.0001 grams, put it in a 100 ml beaker and add about 20 ml of distilled water to heat and dissolve, then transfer to a separatory funnel, extract with ether or petroleum ether several times until ether or The petroleum ether is colorless (if there is a serious emulsification, a few milliliters of ethanol can be added for demulsification). The extracts of diethyl ether or petroleum ether were combined, and diethyl ether or petroleum ether was distilled off on a water bath, and dried at 105 ° C to constant weight. The content of unsaponifiable (or neutral oil) can be calculated according to the following formula
Extract weight (g)
Unsaponifiable (or neutral oil) content%=—————————×100
Sample weight (g)
(III) Determination of fatty acid acid value
Reagents. Ethanol; phenolphthalein; 0.5N potassium hydroxide in alcohol standard solution.
operating. Take a fatty acid sample of about 0.5, and weigh it to 0.0001 g. Dissolve it in a 250 ml flask with 20-30 ml of neutral ethanol, add 2-3 drops of phenolphthalein indicator, and titrate with 0.5 N potassium hydroxide in alcohol standard solution. To the solution is light red. The acid value of the fatty acid is calculated according to the following formula
V×N×56.11
Fatty acid acid price =—————————
Sample weight (g)
Where V is the number of milliliters of potassium hydroxide alcohol standard solution consumed by titration;
N - the equivalent concentration of the potassium hydroxide alcohol standard solution for titration. [next]
(4) Determination of fatty acid saponification price
Reagents. 0.5N HCl; 0.5N alcoholic potassium hydroxide standard solution; substituting bromo thymol blue indicator (or phenolphthalein indicator).
operating. Take about 2 grams of fatty acid sample, weigh accurately to 0.0001 grams, in a 250 ml flask, pipette 25 ml of 0.5N potassium hydroxide alcohol standard solution into a triangular flask, connect the reflux tube, heat reflux After hours, shake the flask to shake the fatty acid completely. After the saponification is completed, add 10 drops of bromo thymol blue indicator (or phenolphthalein indicator), and titrate with 0.5N hydrochloric acid until the blue decolorizing solution is green. (With phenolphthalein indicator, the solution is light red. Turn white). At the same time, do a blank test. The saponification price of fatty acids can be calculated according to the following formula
(V 2 —V 1 )×N×56.11
The saponification price of fatty acids = —————————
Sample weight (g)
Where V 1 - the number of milliliters of hydrochloric acid solution consumed by titration;
V 2 — the number of milliliters of hydrochloric acid solution consumed by the blank test titration;
N - the equivalent concentration of the hydrochloric acid solution.
(5) Determination of fatty acid iodine value
Reagents. Bromo potassium alcohol solution; 15% potassium iodide solution; 0.1 N sodium thiosulfate standard solution; 1% starch solution; bromine water; anhydrous methanol; potassium bromide;
operating. Take fatty acid samples 0.5-5 g (depending on the sample iodine price, the sample size is large, the sample size is small, the sample size is small), the weighing is accurate to 0.0001 g, in the iodine price bottle, add people Dissolve 10 ml of chloroform, pipette 25 ml of bromo methanol solution into the iodine price bottle, add half of the potassium iodide solution in the iodine price bottle after half an hour, let stand for 10 minutes and then add 70 ml of distilled water. The precipitated iodine was titrated with a 0.1 thiosodium sulphate standard solution, and when the solution was pale yellow, a solution of 1-2 ml of the starch solution was added, and the 0.1 N sodium thiosulfate standard solution was continuously titrated until the blue color disappeared. At the same time, do a blank test. The iodine value of fatty acids can be calculated according to the following formula
(V 2 —V 1 )×N×0.1269×100
The iodine value of fatty acids =——————————————
W
Wherein V 1 - the number of milliliters of sodium thiosulfate standard solution consumed by titration;
V 2 — the number of milliliters of sodium thiosulfate standard solution consumed during the blank test;
N - the equivalent concentration of the sodium thiosulfate standard solution for titration;
0.1269 - milliequivalent of iodine;
W——sample weight, gram.
(6) Determination of fatty acid hydroxyl number
Reagents. Pyridine (secondary product, absolutely anhydrous); acetic anhydride; 0.5N sodium hydroxide solution; 0.1% phenolic acid alcohol solution; acetic anhydride pyridine solution.
operating. Take about 0.5g of fatty acid sample and weigh it to 0.0001g. In a iodine price bottle, pipette 10ml of pyridine acetate solution into the iodine price bottle, wet the stopper with pyridine, then plug the iodine. The price bottle was placed on a boiling water bath for three hours. After the reaction was completed, the solution in the iodine price bottle was diluted with 100 ml of distilled water, and phenolphthalein was used as an indicator, and titrated with a 0.5 N sodium hydroxide standard solution until the solution was reddish. At the same time, do a blank test. The hydroxyl value of fatty acids is calculated according to the following formula
(V 2 —V 1 )×N×56.11
Fatty acid hydroxyl price =————————————
W
Where V 1 is the number of milliliters of sodium hydroxide standard solution consumed by titration;
V 2 - the number of milliliters of sodium hydroxide standard solution consumed during the blank test;
N - the equivalent concentration of sodium hydroxide standard solution for titration;
W——sample weight, gram. [next]
(VII) Determination of normal acid and isomeric acid in fatty acids
Reagents. 60-90 ° C petroleum ether; urea; methanol.
operating. Take about 5 grams of fatty acid sample, add 10 ml of 60-90 ° C petroleum ether in a small beaker of 100 ml, and stir and dissolve in a stirrer. In addition, weigh a certain amount of urea (according to the estimated normal acid content of the sample of 3.3 times and an excess of 20%) in another small beaker, weigh 18-20% of the amount of urea mixed with urea, using glass rod The urea methanol mixture is poured into the sample being stirred, stirred for 1.5-2 hours, and the saturated urea solution is used to check whether the urea and the normal acid complex are complete (if 0.1-0.5% of the normal acid is not complexed, then There are white flocculent precipitates). After the reaction was completed, the mixture was allowed to stand for a while, washed with 60-90 ° C petroleum ether, and the precipitate was poured onto the filter paper each time, and washed several times until the petroleum ether washing liquid was colorless. Finally, a small amount of precipitate on the filter paper is washed into the beaker containing the precipitate with distilled water, 50 ml of distilled water is added, and the complex is decomposed by heating (60-70) on the electric furnace. If there is emulsification, a small amount of sodium chloride may be added to the emulsion, and then The mixture was transferred to a separatory funnel, and 60-90 ° C petroleum ether was added to float the organic matter on the liquid surface. The lower portion of the liquid funnel was placed in the separator funnel twice, and washed and combined into the organic matter. The organics were placed on a water bath to distill off the petroleum ether and bake at 105 ° C until constant weight is the normal acid in the sample. The content of normal acid and isomeric acid in fatty acids can be calculated according to the following formula
Beaker and normal acid weight (g) - beaker weight (g)
Normal fatty acid%=——————————————————×100
Sample weight (g)
Isomerized fatty acid %=100%-normal fatty acid%
(8) Fairness of resin acid and fatty acid content in Tal oil
1. Determination of resin acid Reagents. Methanol; diethyl ether; methanolic sulfuric acid mixture (1 part concentrated sulfuric acid and 4 parts of methanol); 0.5N potassium hydroxide alcohol standard solution; a-naphtholquinone indicator; 1N sulfuric acid; anhydrous sodium sulfate; saturated sodium chloride solution.
operating. Weigh about 5 grams of the Tar oil sample, dissolve it in 25 ml of methanol, add 10 ml of methanolic sulfuric acid mixture, and boil it on the water bath for 2 minutes according to the reflux tube. At this time, the fatty acid is esterified to form fatty acid methyl ester. The resin acid is still the free acid. After cooling, 20 ml of a saturated sodium chloride solution was added, and the mixture was poured into a separating funnel, and the mixture was washed three times with diethyl ether. The mixture in the separatory funnel was then extracted with diethyl ether, using 20-30 mL of diethyl ether for the first time and 15 mM diethyl ether for the second and third time respectively. The extracts were combined and washed with a saturated aqueous solution of sodium chloride to neutrality. The washed ether extract was titrated in a separatory funnel with a 0.5% hydroxide alcohol standard solution, and the a-naphtholquinone was used as an indicator to drip into a clear green color (the sodium hydroxide alcohol standard solution consumed was A ml). ). Add one more milliliter of potassium hydroxide alcohol standard solution, and then wash the sodium resinate formed by titration with distilled water (50 ml each time with distilled water). The resin may not dissolve sodium in water often, and the fatty acid methyl ester is separated. In order to prevent a small amount of fatty acid methyl ester from being mixed into the water washing solution, the aqueous solution may be extracted once with diethyl ether, and the fatty acid methyl ester is extracted into the water washing liquid, and the aqueous solution may be extracted once with diethyl ether, and the extracted product is mixed with the fatty acid methyl ester and mixed into the ether layer of the water washing liquid. As a sample for determining the fatty acid content. To the aqueous resin sodium salt solution, 25 ml of 1 N sulfuric acid was added, at which time the resin acid was precipitated, and then the resin acid was extracted three times with diethyl ether. The extract was combined in a 250 ml flask, and dried over 5 g of anhydrous sodium sulfate. Then, the ether solution was filtered off, and the mixture was evaporated to diethyl ether. The residue was a resin acid, which was dried to constant weight at 105 ° C and weighed. The content of resin acid in Tal oil can be calculated according to the following formula
Resin acid weight (g)
Resin acid % in Tal oil = —————————×100
Sample weight (g)
(Note: 2 mg of indicator weight is subtracted from the weight of the resin acid)
The acid value of the resin acid can be calculated from the above-mentioned diethyl ether extract in the amount of A milliliter consumed by the titration of the potassium hydroxide alcohol standard solution:
N×V A ×56.11
Resin acid price = —————————
Resin acid weight (g)
Where N is the equivalent concentration of the potassium hydroxide alcohol standard solution for titration;
V A - The ether extract was consumed in a milliliter amount with a potassium hydroxide alcohol standard solution. [next]
2. Determination of fatty acids Reagents. 0.5N potassium hydroxide alcohol standard solution; a-ceaphenol oxime indicator; 0.5N sulfuric acid standard solution was distilled off in a water bath, and 40 ml of 0.5N potassium hydroxide alcohol standard solution was added to the residue, and the reflux tube was pressed. Boil for 1 to 1.5 hours on a water bath to saponify. After cooling, add 0.2 ml of a-caephenolphthalein indicator, back-titrate with 0.5N sulfuric acid standard solution, and drip until the green color disappears (the amount of sulfuric acid standard solution consumed is B ml). After the titration, the mixture was poured into a separatory funnel, 25 ml of 1 N sulfuric acid was added, the fatty acid was precipitated, the fatty acid was extracted three times with diethyl ether, and the three ether extracts were combined in a 250 ml flask, and 5 g of anhydrous sodium sulfate was added. After drying, the ether solution was filtered off, and the ether was evaporated on a water bath. The residue was a fatty acid, which was dried to constant weight at 105 ° C and weighed. The fatty acid content can be calculated according to the following formula
Fatty acid weight (g)
Fatty acid%=—————————×100
Sample weight (g)
The acid value of fatty acids can be calculated according to the following formula
(N 1 ×40-N 2 ×V B )×56.11
Fatty acid acid price =—————————————
Fatty acid weight (g)
Wherein N 1 is the equivalent concentration of the potassium hydroxide alcohol standard solution for the fair use;
N 2 - the equivalent concentration of the reverse titration sulfuric acid standard solution;
V B - the amount of B ml in the counter-titration end point sulfuric acid standard solution.
(9) Determination of free base in fatty acid soap
Reagents. Ethanol; 0.1N hydrochloric acid standard solution; phenolphthalein indicator.
operating. Take fatty acid soap 2, and weigh it to 0.0001g. In a conical flask, add 30ml of neutral ethanol to dissolve the sample (slightly heated when insoluble), add 2-3 drops of phenolphthalein indicator, use 0.1N hydrochloric acid standard The solution titration red disappears. The content of free base in fatty acid soap can be calculated according to the following formula
W×N×40
Free base % of fatty acid soap =————————×100
Sample weight (g)
Where V is the number of milliliters of hydrochloric acid standard solution consumed by titration;
N - the equivalent concentration of the hydrochloric acid standard solution for titration.
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