Part 20 (1/2)

~Resinous and Tarry matters~ are not unfrequently present They are left insoluble on dissolving the sa water The separation is more perfect if the hot solution be exactly neutralised by caustic soda

~Sulphuric Acid, Hydrochloric Acid, and Oxalic Acid~, and their salts are detected by adding to the filtered aqueous solution of the sample solutions of the picrates of barium, silver, and calciu picric acid with the carbonates of the respective : other soluble salts of these methods may be substituted for the picrates, but they are less satisfactory

~Nitric Acid~the saanic Impurities and Picrates of Potash and Sodiunition

~General Impurities and Adulterations~ rraduated tube with 25 cc of ether, the pure acid dissolves, while any oxalic acid, nitrates, picrates, boric acid, aluar, &c, will be left insoluble, and after removal of the ethereal liquid, may be readily identified and determined For the detection and determination of water and of oxalic acid, 50 cc of wararthe residue insoluble in ether or benzene with rectified spirit, in which sugar and boric acid alone will dissolve If boric acid be present, the alcoholic solution will burn with a green fla point (122 C) Their calcium salts are less soluble than the picrate, and may be approximately separated fro the hot saturated solution of the sample with excess of li the acidulated aqueous solution by agitation with ether or benzene, and subsequently re off the solvent It may also be precipitated as the potassium salt

~Potassiu solution of picric acid is neutralised by carbonate of potash, this salt is thron in yellow crystalline needles, which require 260 parts of cold or 14 parts of hot water for their solution In alcohol it is much less soluble

~Ammonium Picrate~ is more soluble in water than the above, and sodium picrate is readily soluble in water, but nearly insoluble in solution of sodium carbonate

~Picrates of the Alkaloids~--Picric acid forms insoluble salts with many of the alkaloids, and picric acidmanner:--To the solution of picric acid, or a picrate, add a solution of sulphate of cinchonine acidulated with H_{2}SO_{4} The precipitated picrate of cinchonine [C_{20}H_{24}N_{2}O(C_{6}H_{2}N_{3}O_{7})_{2}] is washed with cold water, rinsed off the filter into a porcelain crucible or dish, the water evaporated on the water bath, and the residual salt weighed Its weight, ives the quantity of picric acid in the sample taken

~analysis of Glycerine~[A] Glycerine that is to be used for the lycerine should have a ravity of 1261 at 15 C This can be deterravity balance, or by using an ordinary specific gravity bottle

One of 10 or 25 cc capacity is very convenient

[Footnote A: See also Sulman and Berry, _analyst_, xi, 12-34, and Allen's ”Coanic analysis,” vol ii, part i]

~Residue~[A] left upon evaporation should not be rlycerine, and evaporate it at a temperature of about 160 C in a platinuht is obtained Afterwards incinerate over a bunsen burner, and weigh the ash

[Footnote A: Organic matter up to 6 per cent is not always prejudicial to the nitrating quantities of a glycerine]

~Silver Test~ A portion of the sahing bottle, and a quarter of its bulk of N/10 silver nitrate solution added to it, then shake it, and place in a dark cupboard for fifteen minutes It must be pronounced bad if it becomes black or dark broithin that time (acrolein, forlycerine for pharlycerine heated to boiling with 1 cc of ammonia solution and three drops of silver nitrate solution ive neither colour or precipitate within five lycerine are poured from a beaker into a ravity 153) and sulphuric acid (184), mixed in the proportions of 3 HNO_{3} to 5 H_{2}SO_{4} (about 400 cc of e beaker, and held in the right hand in a basin of water, and the glycerine slowly poured into them from a smaller one held in the left A constant rotatory iven to the beaker in which the nitration is perforlycerine has been added, and the er, it is poured into a separator, and allowed to stand for soood one, have separated from the mixed acids in ten lycerine and the acid should be clear and sharp, neither should there be any white flocculent matter suspended in the liquid The excess of acids is non off, and the nitro-glycerine shaken once or tith a warm solution of carbonate of soda, and afterwards ater alone The nitro-glycerine is then drawn off into a weighed beaker, the surface dried with a piece of filter paper, and weighed; 100 parts of a good glycerine should yield about 230 of nitro-glycerine A quicker lycerine, of which the specific gravity is already known, nitrate as before, and pour into a burette, read off the volulycerine in cc and lycerine), thus: 10 grrlycerine The points to be noted in the nitration of a salycerine are: the separation should be sharp, and within half an hour or less, and there should be no white flocculent matter formed, especially when the carbonate of soda solution is added

~Total Acid Equivalent~ Mr GE Barton (_Jour Amer Chelycerine are diluted to 300 cc

in a beaker, a few drops of a 1 per cent solution of phenolphthalein and 10 cc of nor, the liquid is titrated with norhly determined)

~Neutrality~ The salycerine thus: 50 cc of glycerine mixed with 100 cc of water and a few drops of alcoholic phenolphthalein[A] are titrated with hydrochloric acid or sodium hydroxide; not more than 03 cc normal hydrochloric acid or normal soda solution should be required to render the salycerines contain from 5 to 10 per cent of sodium carbonate

[Footnote A: Sulman and Berry prefer litmus as indicator]

~Deterlycerine is shaken up with solycerine allowed to settle, drawn off, and the ether washed with three separate lots of water The water must have been recently boiled, and be quite free from CO_{2} All the free fatty acid is now in the ether, and no other soluble acid A drop of phenolphthalein is now added, a little water, and the acidity determined by titration with deci-normal baryta solution, and the baryta solution taken calculated as oleic acid

~Colycerine are placed in a flask, and to it is added about half a grm of caustic soda in solution

Thesoh dilute H_{2}SO_{4} to render it distinctly acid It is well shaken All the fatty acids go into the ether

The aqueous solution is then removed, and the ether ashed to remove all H_{2}SO_{4} After the addition of phenolphthalein the acid is titrated, and the amount used calculated into oleic acid From this total amount of fatty acids the free fatty acid is deducted, and the quantity of combined fatty acids thus obtained

~I ilycerine:--Lead, arsenic, lime, chlorine, sulphuric acid, thio-sulphates, sulphides, cyanogen coanic acids (especially oleic acid and fatty acids[A]), rosin products, and other organic bodies It is also said to be adulterated with sugar and glucose dextrine Traces of sulphuric acid and arsenic may be allowed, also very small traces indeed of lime and chlorine

[Footnote A: These substances often cause trouble in nitrating, white flocculent ]

The organic acids, for a salycerine in a test tube with alcohol and sulphuric acid, when, if present, compound ethers, such as ethylic for like peaches and the latter of pine-apple, will be fore quantity, will co the sample ater, but s a current of nitrogen peroxide, N_{2}O_{4} (obtained by heating lead nitrate), through the diluted sample, when a white flocculent precipitate of elaidic acid, which is less soluble than oleic acid, will be thron By agitating glycerol with chloroform, fatty acids, rosin oil, and some other impurities are dissolved, while certain others form a turbid layer between the chlorofor the chlorofor it to dryness, a residue is obtained which may be further examined