Acids decinormal solutions

Chlorides, Bromides, and Thiosulphates. — Dissolve 0.2 gm. of potassium iodide in 2 cc. of ammonia water, add 13 cc. of decinormal silver nitrate solution, shake, and filter. On supersaturating the filtrate with nitric acid, the solution should not become so cloudy as to be opaque nor should a dark color develop, within ten minutes. 

About 2 gm. benzyl iodide are weighed into a flask and then 50 ml. 20% alcoholic potash solution are added and the mixture refluxed for about an hour. At the completion of the saponification the contents of the flask are allowed to cool and then transferred to a 500-ml. flask and made up to volume with water. 100 ml. of the resulting solution are placed in a distillation flask and distilled in steam after adding 10 gm. ferric ammonium alum and acidifying with sulphuric acid. By this treatment, the ferric salt is converted to the ferrous condition, liberating iodine which is distilled over into 5% potassium iodide solution. At the end of the distillation, the free iodine in the potassium iodide solution is titrated with a decinormal solution of sodium thiosulphate. From this, the amount of iodine and so the quantity of benzyl iodide in the sample may be calculated. 

The solution for examination should not contain more than 0-05 gm. hydrocyanic acid. It is treated with a few ml. of sodium hydroxide solution and 0-5 gm. sodium bicarbonate, and is then titrated with a decinormal solution of iodine until a yellow colour persists. In this case it is unnecessary to use starch as indicator ... 

In carrying out this determination, a weighed quantity of cyanogen bromide is treated with an excess of hydriodic acid solution, which is prepared by dissolving 10 gm. potassium iodide in 100 ml. of a 5% solution of acetic acid. The iodine liberated is titrated with a decinormal solution of sodium thiosulphate. 

The contents of the flask are then boiled, being taken almost to dryness and taken up with water several times (generally twice) so as to remove the hydrogen peroxide completely. The residue is diluted once more with 50 ml. water and a solution of sodium carbonate added until a slight precipitate is formed, this being then redissolved with a few drops of dilute acetic acid. Excess potassium iodide is added and the liberated iodine is titrated with a decinormal solution of sodium thiosulphate. 

Determination of Chlorosulphonic Acid. About i gm. of the sample is introduced into a small glass bulb which is then sealed in the flame and weighed accurately. This bulb is then placed in a tall glass cylinder of about 150 ml. capacity, containing about 100 ml. water. The cylinder is stoppered tightly and shaken violently so as to break the bulb, and then allowed to stand until the cloud which first forms in the cylinder completely disappears. The contents are then transferred to a 500 ml. flask and made up to volume. 200 ml. of the solution are then titrated with a decinormal sodium hydroxide solution, to the methyl-orange end-point, so as to obtain the total hydrochloric and sulphuric acid content. In another 200 ml. the hydrochloric acid is titrated with a decinormal solution of silver nitrate in presence of a few drops of potassium chromate solution, after addition of excess of pure calcium carbonate. 

A 6 per eent. solution of hydrochloric acid. (2.) A decinormal solution of sodium thiosulphate. 

Hence, particular precautions must be taken when we prepare permanganate solutions. The most often used solution contains 1/50 mol/L (decinormal solution). They must be standardized before use. For their standardization, we can use some standard reducing inorganic substances such as ferrous salts, arsenious acid, and sodium thiosulfate. We can also use reducing organic substances such as oxalic acid and its derivatives. 

One gram of Ceylon citronella oil or 0 5 grams of Java citronella oil is mixed with 10 c.c. of a freshly prepared 2 per cent, alcoholic solution of redistilled phenylhydrazine and allowed to stand for one to one and a half hours in a flask of about 50 c.c. capacity closed with a glass stopper. Twenty c.c. of decinormal hydrochloric acid is then added, thoroughly... 

Dissolve 1 gm. of the cafminic acid in 100 cc. of water and add one drop of this solution to a solution of 5 gm. of ammonium chloride in 50 cc. of water. The addition to this latter solution of one drop of decinormal potassium hydroxide solution should cause a change in color from yellowish-red to violet-red. 

Quantitative Determination. — Dissolve 1 gm. of iodic acid in water and dilute to 100 cc. Dilute 10 cc. of this solution with 50 cc. of water, and add 2 gm. of potassium iodide and 5 cc. of dilute sulphuric acid. Titrate the liberated iodine with decinormal sodium thiosulphate solution, using starch solution as indicator. 

Volatile Acids, — Mix 30 cc. of the phosphoric acid with 50 cc. of water in a distilling flask. Distil off 50 cc., and titrate the distillate with decinormal potassium hydroxide solution, using methyl orange as indicator. Not more than 0.1 cc. of the decinormal alkali solution should be required. 

Substances Oxidizable by Permanganate. (Nitrous and Sulphurous Acids). — Dilute 15 cc. of sulphuric acid with (50 cc. of water, and color the solution by adding 1 drop of decinormal potassium permanganate solution. The pink color should not disappear within three minutes. 

Quantitative Determination. — Weigh off 10 gm. of sulphurous acid in a measuring flask of 100 cc. capacity, and fill with boiled water up to the mark. Allow the fluid to run from a burette into 30 cc. of decinormal iodine solution, constantly shaken, until decoloration ensues. To effect this not more than 16.2 cc. of the acid solution should be required. 

Cyanogen, Chlorine, and Bromine.—Shake 0.5 gm. of powdered iodine with 20 cc. of water, and filter. To 10 cc. of the filtrate, add, drop by drop, decinormal sodium thiosulphate solution until decolorized, then add a granule of ferrous sulphate, 1 drop of ferric chloride solution and 2 cc. of sodium hydroxide solution. Warm to about 60° C., and add 10 cc. of hydrochloric acid. The liquid should not acquire a blue color. Filter, and to 10 cc. of the filtrate add 1 cc. of ammonia water, 5 drops of silver nitrate solution, and again filter. On adding to the filtrate 2 cc. of nitric acid no precipitate, and not more than an opalescent turbidity, should develop. ... 

Nitrogen. — Dissolve 10 gm. of reduced iron in a mixture of 20 cc. of concentrated sulphuric acid (sp. gr. 1.84) and 200 cc. of water, with the aid of heat. Allow to cool, and when cold add 100 cc. of sodium hydroxide solution (sp. gr. 1.3), and distil off about 50 cc., collecting the distillate in a receiver containing about 20 cc. of water and 2 to 3 cc. of decinormal hydrochloric acid. Titrate the distillate with decinormal potassium hydroxide, using methyl orange as indicator. The ammonia should not have neutralized more than 0.2 cc. of the acid. 

Quantitative Determination. — Place 0.5 gm. of the finely powdered iron sulphide in a retort, in the tubule of which is fixed a funnel-tube provided with a glass cock. After connecting the retort with a receiver containing 50 to 100 cc. of decinormal iodine solution, allow to flow into the retort, through the funnel-tube, a mixture of 20 cc. of water and 20 cc. of dilute sulphuric acid close the stop-cock, and heat to boiling. After the decomposition of the iron sulphide is complete, and the hydrogen sulphide has been entirely driven off (the iodine solution must not be fully decolorized), determine the excess of iodine by means of decinormal sodium thiosulphate. 

Add 2 drops of the indicator solution to 100 cc. of distilled water. On the addition of 0.05 cc. of decinormal potassium carbonate, the light-brown color of the water should pass into pink on the further addition of 0.05 cc. of decinormal hydrochloric acid, the color should change to a golden yellow. 

Neutrality. — Dissolve 10 gm. of the neutral potassium iodide in 50 cc. of water, in a stoppered, flint-glass bottle, overlay with 30 cc. of ether, and add 3 drops of iodeosin solution. After vigorously shaking, the aqueous layer will exhibit a pale-red color which disappears on adding 1 drop of decinormal hydrochloric acid and thoroughly shaking. 

Oxidimetric To 50 cc. of the solution made for test a, add 6 to 8 cc. of concentrated sulphuric acid, heat the liquid to about 60° C., and titrate with decinormal potassium permanganate. 

Quantitative Determination. — Dissolve 1.5 gm. of silver nitrite in water and dilute to 500 cc. Make a mixture containing 18 to 19 cc. of decinormal potassium permanganate solution, 20 cc. of dilute sulphuric acid, and 300 cc. of water, heat it to 40 to 50° C., and run the nitrite solution into it until the pink color just disappears. Care must be taken towards the end to introduce the nitrite solution very slowly, because the change from pink to colorless always requires some time. 

Uranous Salt. — The solution of 1 gm. of uranium nitrate in 20 cc. of water and 1 cc. of dilute sulphuric acid should be colored red on the addition of 0.1 to 0.2 cc. of decinormal potassium permanganate. 

As soon as the zinc has dissolved, add to the solution, drop by drop, decinormal potassium permanganate. Not more than 0.1 cc. should be required to produce a distinct pink color. Should more of the permanganate solution be required, the dilute sulphuric acid (15 cc. of sulphuric acid and 60 cc. of water) should be titrated for the purpose of control, without zinc, using the same solution of decinormal potassium permanganate. 

Quantitative. The acidity is estimated as follows 25 grams of the product are made into a paste with 30 c.c. of water and titrated, with shaking, with N/10-caustic soda solution until a drop of the starch suspension, when placed on a filter-paper folded several times so as to absorb the water, is no longer coloured red by tincture of litmus. The acidity is expressed in c.c. of decinormal alkali per 100 grains of starch. 

Total Acidity.—50 or 100 c.c. of the beer, freed from the bulk of the carbon dioxide, are heated for half an hour at 400 to expel the residual gas and are then titrated with N/io-sodium hydroxide, neutral litmus paper or phenolphthalein being used as indicator when phenolphthalein is employed, it is well to add a slight excess of the alkali and then to run in N/10-sulphuric add until the red coloration disappears. When, however, the liquid is too highly coloured to allow accurate observation of the point of neutrality, the procedure is as follows to 20 c.c. of distilled water, previously boiled, are added 10-12 drops of alcoholic phenolphthalein solution and 0 2 c.c. of N/io-sodium hydroxide. The beer is then titrated with the decinormal alkali and, after each addition of the latter, six drops of the liquid are added to one drop of the indicator prepared as above, placed in the depression of a porcelain plate the titration is finished when this indicator is no longer decolorised in this way. The acidity is usually 1 Race Joum. Soc. Chem. Industry, 190S, XXVII, p, 544. 

The solution possesses the characteristic odour and oxidising properties of the gas. In dilute acid solution ozone is much more stable and the absorption coefficient m decinormal sulphuric acid has been experimentally determined as 0 487 at 0.1... 

Hypophosphite and phosphite may also be determined by oxidation with iodine. In alkaline bicarbonate solutions phosphites are oxidised quickly to phosphates, while hypophosphites are hardly affected, i.e. they do not use any measurable amount of decinormal iodine after standing for two hours at ordinary temperatures. In acid solution hypophosphorous acid is slowly oxidised to phosphorous acid, but no further, according to the equation... 

A phosphite solution of about Mj 10 concentration is placed in a stoppered flask with an excess of sodium bicarbonate saturated with carbonic acid and an excess of decinormal iodine solution and allowed to stand for about an hour. It is then acidified with acetic acid and the excess of iodine is back-titrated with decinormal biearbonate-arsenite. 

A hypophosphite solution is acidified with dilute sulphuric acid, treated with a known amount, in excess, of decinormal iodine solution and allowed to stand for 10 hours at ordinary temperatures. A cream of NaHCOg is then added until C02 evolution ceases, then fifth-normal NaHC03 solution, saturated with C02, whereby oxidation goes through the next stage, to phosphate. After addition of acetic acid the excess of iodine is titrated with standard arsenite as before. 

Determination of Orthophosphates.—(1) With Silver Nitrate.— This depends upon the precipitation of silver orthophosphate in solutions of low and controlled acidity. In the assay of commercial 85 per cent, phosphoric acid of density 1-710 the syrup is diluted to a convenient volume and an aliquot part is taken which contains about 0-1 gram of H3P04. It is neutralised to phenolphthalein with approximately decinormal alkali (free from chloride). 50 c.c. of decinormal silver nitrate are then added while the solution is kept neutral to litmus by stirring in zinc oxide or a suspension of the hydroxide. The whole or a measured part of the filtered solution is acidified with nitric acid and, after the addition of ferric alum, the unused silver nitrate is titrated with standard decinormal ammonium thiocyanate in the usual manner. Alkali phosphates may also be determined in this way. 

This reaction is also used in the method of Holleman 2 as modified by Wilkie.3 A phosphate solution containing phenolphthalein is reddened by the addition of alkali, then just decolorised with nitric acid. An excess of standard silver nitrate is then added and decinormal sodium acetate and alkali to slight pink colour, followed by 2 c.c. of decinormal H2S04. The solution is diluted and filtered and the excess of silver determined by titration with decinormal ammonium thiocyanate. 

An ammonium phosphomolybdate precipitate is treated as described under (2c) (p. 182) for conversion into MgNH4P04. The washed precipitate of MgNH4P04 may be determined volumetrically by solution in a known quantity in excess of standard hydrochloric acid and baek-titration with decinormal alkali using methyl orange, thus... 

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