Acidity or alkalinity of water extract

Part 4 of ISO 787 specifies the method of determination and Part 3 specifies how the extract should be prepared. The material for testing is extracted in boiling water for 5 minutes and filtered to obtain a clear filtrate. An aliquot of filtered extract is titrated either with hydrochloric acid or sodium or potassium hydroxide solution in the presence of an indicator or evaluated by potentiometric determination. 

The ASTM method differs from ISO in extract preparation which is obtained by a 5 minute extraction at room temperature. The method of determination is based on titration in the presenee of an indicator. The acid used for titration is sulfuric acid. 

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Ibid., Hot-Water Extractable Acidity or Alkalinity of Paper, T-428sa-67. 

The initial acidity or alkalinity of paper is measured conventionally by the pH of the water extract or by the total titratable acidity or alkalinity of the water extract (TAPPI T428 and ASTM D548). The extract for measurement of pH may be prepared as the cold water extract (TAPPI T509) or as the hot water extract (TAPPI T435 and ASTM D778). In the absence of hydrolyzable salts, it may be expected that hot and cold extraction methods will give approximately the same results. If hydrolyzable acid salts (particularly alum) are present, the hot extraction method yields a lower pH because of hydrolysis promoted at the higher temperature to yield free acids. 

Neutral and basic herbicides were extracted from water made alkaline with sodium hydroxide or from soil, with chloroform extracts of soil were cleaned up on basic alumina containing 15% of water. Acidic herbicides were extracted with ethyl ether from water acidified with hydrochloric acid or from an aqueous extract of soil prepared by treatment with 10% aqueous potassium chloride that was 0.05M in... 

Either acid or alkaline hydrolysis can be applied, converting nicotinamide to nicotinic acid. Alkaline hydrolysis releases also the unavailable vitamers providing the estimation of the total niacin content. Acid hydrolysis, instead, is slower than alkaline hydrolysis therefore the former is usually coupled with enzymatic digestion by using takadiastase, papain, and clarase. Extraction with water and dilute sulfuric or hydrochloride acid has been applied to release the vitamers from the matrix without degrading nicotinamide [598]. 

The acidity or alkalinity is measured as the quantity of cubic centimeters of 0.1 N alkali (NaOH or KOH) or acid solution that are required to neutralize an aqueous extract of 100 g pigment under prescribed conditions. Unless otherwise agreed, the pigment is extracted with hot water. If cold water is used, this must be specifically stated. For standards, see Table 1 ( Acidity/alkalinity ). Test reagents 0.5 N HC1 or H2S04, 0.5 N NaOH or KOH, indicators (by agreement). 

Treated papers should maintain at a pH in the range 7 and 8.5. The pH should not be higher than 8.5 to prevent alkaline hydrolysis of cellulose. The acidity or alkalinity may be determined as the amount of water-soluble acidity or as the hydrogen ion concentration (pH) of the paper extract. The pH is more indicative of the stability of paper than is the total acidity. The pH can be determined by either a hot or cold extraction method. In the cold extraction method,... 

The aqueous fraction from the neutral or alkaline liquid-liquid extraction, or another portion of the original sample is prepared for analysis of the sample for lewisite 1 (CAS 541-25-3), lewisite 2 (CAS 40334-69-8), and lewisite oxide (CAS 3088-37-7) (Figure 1, fraction 5). The pH of the sample is adjusted with hydrochloric acid to pH 2, the sample is filtered, and 0.1 ml of a freshly prepared solution containing 3,4-dimercaptotoluene (DMT, CAS 496-74-2) 5 mg ml-1 in acetone is added. The sample vial is shaken vigorously and allowed to stand for 10 min. Then one milliliter of n-hexane is added and the sample is shaken vigorously for 30 s every 10 min for 30 min. The hexane fraction is allowed to separate. The top hexane-water fraction is tiansferred to a new vial and centrifuged. After centrifugation, the hexane fraction is separated, dried, and submitted for analysis. 

Since the environmental history of the book would influence the results obtained from physical property measurements made on the paper, each book was preconditioned in a standard atmosphere (4) before any paper samples were removed. The following physical property measurements were made on the same pages throughout each of the control and dried books tensile breaking strength (5) tensile energy of absorption (6, 7) internal tear resistance (8) thickness (9) and hot-water extract-able acidity or alkalinity (10). 

All the possible degrees of acidity or alkalinity are found in the range between zero and fourteen on the pH scale. This is crucial for us to know, since it is a fact of nature that to make alkaloids soluble in water we must first make them acidic. Conversely, for them to be soluble in an organic solvent, such as ether, we must make them basic or alkaline. Most of the psychoactive substances we are interested in extracting are called "alkaloids," compounds numerically above 7 in pH. Webster s Third New international Dictionary defines the word for us ... 

Prior to chromatographic analysis of foods, acid or alkaline pretreatment is used to liberate nicotinic acid (Hengen and deVries, 1985). Katsui (1972) described a method for determining nicotinic acid in coffee. After extraction with HCl and decoloration with lead carbonate, the solution was spotted on chromatographic paper and developed in a mobile phase of -butanol-ammonia-water (100 2 16). Spots were visualized using cyanogen bromide and benzidine. This procedure is probably applicable to TLC on cellulose. 

Neutral and basic herbicides were extracted from water made alkaline with sodium hydroxide or from soil, with chloroform extracts of soil were cleaned up on a basic alumina containing 15% of water. Acidic herbicides were extracted with ethyl ether from water acidified with hydrochloric acid or from an aqueous extract of soil prepared by treatment with 10% aqueous potassium chloride that was 0.05m in sodium hydroxide and filtration into 4m hydrochloric acid. The concentrated chloroform solution of neutral and basic herbicides was applied to a pre-coated silica gel plate containing a fluorescent indicator and a chromatogram was developed two-dimensionally with hexane-acetone (10 3) followed after drying by chloroform-nitromethane (1 1). The spots were detected in ultraviolet radiation. Atrazine, Barban, Diuron, Linuron, Monouron, Simazine and Trifluralin were successfully separated and were located as purple spots on a green fluorescent backgroimd. The ether extracts were dried over sodium sulphate. 

Method 2. Place a 3 0 g. sample of the mixture of amines in a flask, add 6g. (4-5 ml.) of benzenesulphonyl chloride (or 6 g. of p-toluenesulphonyl chloride) and 100 ml. of a 5 per cent, solution of sodium hydroxide. Stopper the flask and shake vigorously until the odour of the acid chloride has disappeared open the flask occasionally to release the pressure developed by the heat of the reaction. AUow the mixture to cool, and dissolve any insoluble material in 60-75 ml. of ether. If a solid insoluble in both the aqueous and ether layer appears at this point (it is probably the sparingly soluble salt of a primary amine, e.g., a long chain compound of the type CjH5(CH2) NHj), add 25 ml. of water and shake if it does not dissolve, filter it off. Separate the ether and aqueous layers. The ether layer will contain the unchanged tertiary amine and the sulphonamide of the secondary amine. Acidify the alkaline aqueous layer with dilute hydrochloric acid, filter off the sulphonamide of the primary amine, and recrystaUise it from dilute alcohol. Extract the ether layer with sufficient 5 per cent, hydrochloric acid to remove all the tertiary amine present. Evaporate the ether to obtain the sulphonamide of the secondary amine recrystaUise it from alcohol or dilute alcohol. FinaUy, render the hydrochloric acid extract alkaline by the addition of dilute sodium hydroxide solution, and isolate the tertiary amine. 

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