Alkali solubility test

XVI. Alkali Solubility Test. Shake ca 0.5g of the sample for 2mins in a test tube with 5ml... 

Quantitative tests for RDX are described in this Volume under Cyclotrimethylenetrinitramine (RDX), Analytical Procedures Xy Alkali Solubility Test. Shake ca 0,5g of the sample for 2mins in a test tube with 5ml of 10% NaOH soln, filter and acidify the filtrate with coned HCl, Cool the tube under tap w, and rub the inside of the tube with a glass rod, A white ppt, appearing after about 5mins, is a positive test for EDNA and its presence can be confirmed by treating the sample with Thymol Reagent - a brown color is a positive test for EDNA (See also Chart B)... 

Vauquelin (14), A. Klaproth (6), and R. Jameson (5), alkali soluble organic constituents of soil and coal are designated as humic acids/ Collectively, these substances make up an ill-defined series of dark colored, weakly acidic solids which form whenever plant components (such as lignin) are exposed to fungal oxidases, or when coal is allowed to weather or otherwise oxidize. Some evidence now exists that humic acids isolated from these varied sources do indeed contain several common peripheral structures (2, II, 16), but by any more discriminating test, the term possesses little chemical significance or fixed meaning. 

We have repeated this work using purified Ci, Cx, and a low-molecular-weight Cx component (26,46) isolated from T. koningii, but we can find no difference in the alkali-soluble fraction produced by Ci or Cx (Figure 9). Indeed, of the three fractions tested, the low-molecular-weight Cx component produced the largest increase in the portion soluble in alkali. 

Negative substituents enhance the acidic properties of phenols, an effect opposite to that produced with aromatic amines. o and p-Chloro-phenols are considerably stronger acids than phenol itself, and o- and p-nitrophenols are still stronger. Trinitrophenol, picric acid, is a strong acid whose salts are neutral and not decomposed by carbonic acid or by ammonium salts. These salts of picric acid can be salted out of neutral solutions by sodium or potassium chloride. With negatively substituted phenols, it may be possible to separate the phenolate from solutions which are neutral or weakly alkaline to litmus. In doubtful cases, just as with the amines, the precipitated material must be studied to determine whether it is the free phenol or one of its salts. The color of the precipitate gives an indication in the case of the nitrophenols, since the free phenols have only a weak yellow color, whereas the alkali salts are deep yellow. Solubility tests with indififerent solvents may be used in the case of uncolored compounds. Only the free phenol can be separated from acidic solutions. 

Lees and Elsworth International Textile Wool Conference, 1955) drew attention to the fact that wool which has been submitted to an alkaline treatment has a lowered alkali solubility. To avoid this source of error the urea bisulphite test was proposed. Alkali treated wool has a lower solubility in the urea bisulphite reagent, and treatment under acid conditions brings about an increased solubility. These facts make it possible to arrive at an historical deduction of the nature of the cause of any degradation. 

There are two other reasons why alkalis are important. First, in mineral processing, minerals such as chromite require fusing with an alkali to convert the element being extracted into a soluble form. Both sodium carbonate and potassium carbonate are used as fusion mixtures. Second, in the manufacture of glass, silica is fiised with either soda ash or potassium carbonate. In our view, ashes with a very high alkali content, such as those of banana wastes, can be used in place of the commercially-available alkalis. Some tests are under way to confirm this hypothesis. 

Testing Procedures. The tensile properties of dry and wet warp yarns from control and treated samples were measured by ASTM D2256-66T on an Instron Tensile Tester, Model TM using a gauge length of 3 inches and a rate of extension of 33% per minute (Table I). Wrinkle recovery (dry and wet) values were determined by AATCC test method 66-1978 (Table 11). The felting shrinkage and alkali solubilities were determined by the methods outlined by Haron (14) (Table II). 

The mode of action of sulfonamides was greatly clarified by Woods in 1940. It had been shown that tissue extracts, pus, bacteria, and particularly yeast extract contained a heat-stable substance of low molecular weight which would inhibit the action of sulfonamides on bacteria (Stamp, 1939). Woods, recalling that enzymes are inhibited by substances which chemically and sterically resemble their substrates (see Section 9.3.1), adopted this hypothesis that the inhibitory substance in yeast is the substrate of an enzyme widely distributed in nature, and that it resembles sulfanilamide chemically. He found activity was concentrated in an alkali-soluble fraction of yeast, and that it ran parallel to a colour test for an aromatic amino-group. Activity was lost on esterification or acetylation, recovered on hydrolysis, and lost again on treatment with nitrous acid (Woods, 1940). Thus he made it clear that the active substance was an aromatic amino-acid. Because -aminobenzoic acid (/ AB) 2,12, p. 31) is the aromatic amino acid that most resembles sulfanilamide 2.13) he tried it as an inhibitor of bacteriostasis, and found that one molecule could prevent 5000 to 25 000 molecules of sulfanilamide from functioning. 

For better evaluation the hemicellulose flactions were extracted using a sodium hydroxide concentration of 18 and 10% which corre nded to the R18 and RIO values of pulp tests (13). After separation of the alkali-soluble S-fraction and the alkali-insoluble R-flaction the carbohydrate compositions were determined by anion exchange chromatography. The data are presented in Table III. ... 

The above reaction proceeds smoothly under suitable experimental conditions, viz., proper temperature control and acid concentration. The solution of alkyl sulfuric acid may be poured into water, neutralized with excess alkali, and the corresponding alcohol recovered by distillation. When an olefine is treated with concentrated sulfuric acid without special precautions, as in the usual solubility test, only a portion of the compound is converted into a soluble alkyl sulfuric acid, the remaining portion being polymerized to compounds of limited solubility in sulfuric acid. The first step in such a polymerization may be represented thus ... 

A more convenient method for differentiation between the aromatic and paraffin hydrocarbons is the dimethyl sulfate solubility test (page 135). The paraffin hydrocarbons do not dissolve appreciably in this reagent, whereas ai-omatic hydrocarbons in general dissolve in all proportions, diu )robably to the formation of an addition product between fhe ester and f Ikj aromatic nuck us. The aromatic hydrocarbons may be r( ( .over( d from dimethyl sulfate by saponifying the latter with dilute alkali. Thia method of differentiation does not extend to the halogen derivatives of these hydrocarbons. 

Solubility Tests.—Determine the solubility of the unknown in water, dilute alkali, dilute acid, ether, and cold concentrated H2SO4. For details and discussion see Chapters II and VIII. Finally consult the Solubility Table at the end of this text. 

Solubility tests are applied at room temperature (20°-25°). Observations of value may be made b determining solubility behavior in hot solvents but for purposes of classification the results obtained at room temperature are the ones desired. The action of hot acid or alkali will l)e studied subsequently in connection with the homologous tests. 

For a cobalt(ll) salt, the precipitation of the blue->pitik cobalt(II) hydroxide by alkali, or precipitation of black cobalt(II) sulphide by hydrogen sulphide provide useful tests the hydroxide is soluble in excess alkali and is oxidised by air to the brown CoO(OH) . 

There are complications in applying the Hinsberg test to certain amines containing hydroxyl, nitro and carboxyl groups, e.g., p-N-methylamiiiobenzoic acid CHjNHC.HjCOOH (I 4) may behave in this test as a primary amine (soluble in alkali) so that it is essential to consider the properties of the original compound in conjunction with the results of the test. 

Alkali or alkaline-earth salts of both complexes are soluble in water (except for Ba2[Fe(CN)g]) but are insoluble in alcohol. The salts of hexakiscyanoferrate(4—) are yellow and those of hexakiscyanoferrate(3—) are mby red. A large variety of complexes arise when one or more cations of the alkah or alkaline-earth salts is replaced by a complex cation, a representative metal, or a transition metal. Many salts have commercial appHcations, although the majority of industrial production of iron cyanide complexes is of iron blues such as Pmssian Blue, used as pigments (see Pigments, inorganic). Many transition-metal salts of [Fe(CN)g] have characteristic colors. Addition of [Fe(CN)g] to an unknown metal salt solution has been used as a quaUtative test for those transition metals. 

Adds.—A free acid may be at once identified by its solubility in a holution of sodium carbonate and by being reprecipitated by concentrated hydrochloric acid. If a metal has been dis-coveied in the piehminary examination, a careful examination must be made for an organic acid. As the substance is insoluble ill water the metal will probably not be an alkali metal. Boil the substance with sodium carbonate solution. The sodium salt of the acid passes into solution and the metallic carbonate IS precipitated. Filter boil the filtrate with a slight excess of nitric acid, add excess of ammonia and boil until neutral, tests may then be applied in order to identify one of the common acids and the ni.p. determined but beyond this it is impossible to carry the investigation in a limited time. 

Glyceryl acetate, which is an artificial ester commonly used in the adulteration of bergamot oil, is detected fairly easily on account of its high solubility in dilute alcohol. The test is carried out as follows Ten c.c. of bergamot oil and 20 c.c. of 5 per cent, alcohol are well shaken in separating funnel, and after the solutions have separated and become clear the watery solution is run off and filtered. Ten c.c. of the filtrate are exactly neutralised with deci-normal alkali, and then 5 c.c. of seminormal alkali run in, and the whole saponified under a reflux condenser for one hour. In the case of pure bergamot oil 0 1 or at most 0 2 c.c. of semi-normal alkali will have been used up by the saponification, whilst each 1 per cent, of glyceryl triacetate present in the oil will be represented by practically 0 5 c.c. of semi-normal alkali. 

Whole article tests Grain tests are open to the criticism that they do not necessarily reflect the behaviour of the finished product in service, hence various tests on complete glass articles have been developed. These are normally carried out under accelerated conditions, and on completion various relevant factors are determined, such as loss in weight, alkali or other constituents extracted, the weight of soluble and insoluble materials in the extract and an assessment of surface condition. The advent of the electron microscope as a standard tool has made the latter study much more objective. 

Benzoic acid is sparingly soluble in water (which is a disadvantage) and must therefore be dissolved in 95 per cent ethanol. The mode of use is similar to that already described for potassium hydrogenphthalate (Section 10.27, Procedure B). For a 0.1 M solution, of, say, sodium hydroxide, weigh out accurately 0.4 g portions of the acid into a 250 mL conical flask, add 10- 20 mL of ethanol, shake until dissolved, and then titrate the solution with the strong alkali using phenolphthalein as indicator. A blank test should be made with the same volume of ethanol and the indicator deduct, if necessary, the volume of the alkali solution consumed in the blank test. 

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