Cooley's Cyclopaedia of Practical Receipts Volume I Part 143

Mr Shuttleworth, writing to the 'Canadian Pharmaceutical Journal,'

says:--"In regard to the restoration of chloroform which has become spoiled, I would recommend that the chloroform be well agitated with a dilute solution of hyposulphite of soda.

"It should then be separated by means of a gla.s.s funnel from the supernatant liquid, and again washed; this time with simple water. After being separated the chloroform should be pa.s.sed through filtering paper to free it from traces of moisture, when it will be found much improved and comparatively sweet, good enough in any case for external use.

"There are, of course, certain other impurities of chloroform which the hyposulphite will not remove. These are of a more stable character, and as they possess a higher boiling point than chloroform, may be separated by distillation, or by treatment with sulphuric acid in the usual manner."

_Uses, Action, &c._ Chloroform is anodyne, antispasmodic, sedative, stimulant, and anaesthetic. In small doses (5 to 12 or 15 drops, in water, mixed with a little syrup or mucilage) it is employed in spasmodic disorders, and as a stimulant and diaph.o.r.etic. It is now chiefly used as an anaesthetic to produce insensibility to pain during surgical operations.

The dose for inhalation is 1 fl. dr., which is repeated, in a few minutes, if no effect is produced, until 3 fl. dr. have been thus exhibited; the effects being carefully watched, and the source of the chloroform vapour removed as soon as a sufficient degree of anaesthesia is produced, or any unpleasant symptoms develop themselves.

Chloroform in large doses depresses the heart's action, and causes profound coma, and death. It is therefore dangerous in all cases complicated with diseases of the heart or brain, or any visceral affections of a congestive character.

The treatment of asphyxia from chloroform is--the horizontal position, cold affusion to the head and spine, artificial respiration, and, if possible, either the application of electricity, or the inhalation of protoxide of nitrogen or oxygen gas, largely diluted with atmospheric air.

_Concluding Remarks._ The preparation of chloroform is not unattended with danger, and frequently miscarries in careless or inexperienced hands. This arises chiefly from the violent reaction which immediately follows the application of the heat. The common plan is attended with danger of explosion, or of the liquid in the still being forced over into the receiver, owing to the extraordinary rapidity with which the vapours are eliminated, and the ingredients, in consequence, swell up. A method which is successfully adopted on the large scale is to employ a very broad and shallow capsule-shaped still, having a flat rim round it, with a head or capital furnished with a corresponding rim at its lower part. In use, a flat, endless band of vulcanised india rubber is placed between the two rims, which are then held air-tight together by means of small, iron clamps. The application of heat is also delayed for some time after the admixture of the spirit with the other ingredients, and the process is interrupted as soon as the first violence of the reaction has subsided, by which time the whole product of chloroform will have pa.s.sed over into the receiver. If the distillation is continued beyond this point, the remaining product is water. On the small scale, a very capacious, flat-bottomed retort or cucurbit should be employed. A similar condenser may be used to that noticed under ether.

=CHLOROFORMIC ANODYNE= (George Harley) is said to be an alcoholic tincture of opium with prussic acid and chloroform.

=CHLOROHYPONITRIC GAS= (NOCl) and =CHLORONITROUS GAS= (N_{2}O_{2}Cl_{4} are two peculiar compounds, formed when nitric acid and hydrochloric acid are mixed.

=CHLOROMETER.= _Syn._ CHLORIM'ETER. An instrument or apparatus employed in chlorometry. The chlorometers in common use are graduated measures and tubes precisely similar to those used in ACIDIMETRY, ALKALIMETRY, &c.

=CHLOROMETRY.= _Syn._ CHLORIM'ETRY. The estimation of the available chlorine in the bleaching powder of commerce, which is valued and sold in this country by its per-centage of that element. The plans generally adopted are applicable to the so-called chlorides of soda and pota.s.sa, as well as to the ordinary bleaching powder, chloride of lime. Most of them depend on the oxidising effect of water when undergoing decomposition through the action of chlorine.

_Dalton's Process._ The test solution is prepared as follows:--Pure protosulphate of iron (previously dried by strong pressure between the folds of cloth or bibulous paper), 78 gr., are dissolved in distilled water, 2 oz., and a few drops of hydrochloric or sulphuric acid added.

This quant.i.ty of protosulphate requires for complete peroxidation just the quant.i.ty of oxygen liberated by 10 gr. of chlorine; in other words, the solution exhibits the indirect effect produced by exactly 10 grains of the bleaching element.

Exactly 50 gr. of the sample of chloride of lime to be examined are next weighed, and well mixed in a gla.s.s or wedgwood mortar with tepid water, 2 oz.; and the mixture poured into a graduated tube or chlorometer. The tube is next filled up to 0, or zero, with the was.h.i.+ngs of the mortar, and the whole well mixed, by placing the thumb over the orifice and shaking it.

The solution of chloride of lime, thus formed, is next gradually and cautiously added to the solution of sulphate of iron, previously noticed, until the latter is completely peroxidised, which may be known when it ceases to be affected by a solution of red prussiate of potash. When a drop of the latter test, placed upon a white plate, ceases to give a blue colour on being touched with the point of a gla.s.s stirrer or rod dipped in the liquor under examination, enough of the solution of the chloride has been added. The number of measures thus consumed must now be carefully read off from the graduated scale of the chlorometer, from which the richness of the sample may be estimated as follows:--As 100 of the chlorometer divisions contain exactly 50 gr. of the chloride under examination, each measure will contain only 1/2 gr., and, consequently, the number of measures consumed will represent half that number of grains of the chloride examined; and the weight of the chloride thus used will have contained 10 gr. of chlorine--the constant quant.i.ty of that substance required to peroxide the test solution of sulphate of iron. Thus:--If 80 measures of the liquor in the chlorometer have been consumed, this quant.i.ty will represent 40 gr. of chloride of lime, and 10 gr. of chlorine. By dividing 1000 by this number, the per-centage of chlorine will be obtained. In the present instance this would be--

1000 ---- = 25% 40

_Crum's Process._ Equal weights of water and hydrochloric acid are mixed together, and cast-iron borings digested in the diluted acid until saturation is complete; a large excess of iron being purposely employed, and the liquid kept at the heat of boiling water for some time. One measure of the solution, marking 40 on Twaddell's scale (sp. gr. 1200), is then mixed with an equal quant.i.ty of acetic acid (sp. gr. 1048). This forms the test-liquid. When mixed with 6 or 8 parts of water it is quite colourless, but chloride of lime occasions the production of peracetate of iron, which gives it a red colour.

The above proof-solution is next poured into 12 two-oz. vials, of exactly equal diameters, to the amount of 1/9th of their capacity; these are filled up with bleaching liquid of various strengths; the first at 1/12th of a degree of Twaddell, the second 2/12ths, and so on up to 12/12ths of 1. They are then well corked up, and, after agitation, arranged side by side on a tray, furnished with holes to receive them. (See _engr._) To ascertain the strength of an unknown sample of bleaching liquor, the proof-solution of iron is put into a phial, exactly similar to the 12 previously used, and in precisely the same proportion (1/9th). The phial is then filled up with the bleaching liquor, well shaken, and placed beside that one of the 12 already prepared which it most resembles in colour. The number on that phial expresses the strength of the sample under examination, in twelfths of a degree of Twaddell's hydrometer.

[Ill.u.s.tration]

_Obs._ The preceding method is admirably suited for weak solutions, such as are employed for bleaching textile fabrics, and is well adapted (from its simplicity) to the purposes of practical men. Indeed, it is quite astonis.h.i.+ng to see with what ease and accuracy it is applied by unlettered operatives. This gives it great practical value. It has been for some time in extensive use in the bleaching houses of Scotland.

TABLE _exhibiting the quant.i.ty of Bleaching Liquid, at 6 on_ TWADDELL'S _scale_ (_sp. gr._ 1030), _required to be added to a weaker liquor, to raise it to the given strengths. Adapted from_ MR CRUM'S _table by_ MR COOLEY.

----------------------------------------------- Proportions required.

Strength Required ----------------------- of Sample Strength. Given Liquor in 1/12. Sample. at 6.

-----------+-----------+-----------+----------- Parts. Part.

Water. 8/12 8 1 1 " 9-1/4 1 2 " 11 1 3 " 13-1/2 1 4 " 17 1 5 " 23 1 6 " 35 1 7 " 71 1 Water. 6/12 11 1 1 " 13-1/2 1 2 " 17 1 3 " 23 1 4 " 35 1 5 " 71 1 Water. 4/12 17 1 1 " 23 1 2 " 35 1 3 " 71 1 Water. 3/12 23 1 1 " 35 1 2 " 71 1 ------------------------------------------------

According to Mr Crum, the range of strength within which cotton is "safe"

is very limited. A solution at 1 of Twaddell's scale (sp. gr. 1005) is not more than safe, while one at 1/2 is scarcely sufficiently strong for the first operation on stout cloth, unless it is packed more loosely than usual.

_Gay-Lussac's Indigo Process._ One part of the best indigo is dissolved in 9 parts of strong sulphuric acid by the aid of a gentle heat; this solution is then mixed with distilled water, in such proportion that 1 volume of chlorine gas shall exactly decolour 10 volumes of this solution.

Each measure so decoloured is called a degree, and each degree is divided into fifths. 5 gr. of the best chloride of lime, dissolved in 500 gr.

measures of water, possess the above power, and indicate 10 or proof; or in other words, will decolour 10 times its volume of the indigo solution.

_Obs._ This method of chlorometry is objectionable, and liable to error, from the indigo solution altering by keeping. When, however, the proper precautions are used, it may be safely trusted for weak bleaching liquors.

_a.r.s.enious Acid Process._ This depends on the conversion, by oxidation, of a.r.s.enious acid into a.r.s.enic acid, in the presence of chlorine and water.

To prepare the test-liquor, pure a.r.s.enious acid, 100 gr., are dissolved in about 4 fl. oz. of pure hydrochloric acid (free from sulphurous acid), and the solution diluted with water until, on being poured into a graduated 10,000 grains-measure-gla.s.s, it occupies the volume of 7000 grains measure marked on the scale. Each 1000 grains measure of this liquid now contains 1429 gr. of a.r.s.enious acid; corresponding to 10 gr. of chlorine, or 1/10th gr. of chlorine for every division or degree of the scale of the chlorometer.

100 gr. of the chloride of lime to be examined are next dissolved in water as before, and poured into a tube graduated up to 2000 grains measure. The whole is now well shaken, in order to obtain a uniformly turbid solution, and half of it (1000-grains-measure) transferred to a graduated chlorometer, which is, therefore, thus filled up to 0, or the zero of the scale, and contains exactly 50 gr. of the chloride of lime under examination; whilst each degree or division of the scale contains only 1/2 gr.

1000 grains measure of the a.r.s.enious acid test-liquor are now poured into a gla.s.s beaker, and a few drops of solution of sulphate of indigo added in order to impart a faint but distinct blue colour to it; the gla.s.s is then shaken so as to give a circular movement to the liquid, and whilst it is whirling round, the chloride-of-lime solution from the chlorometer is gradually and cautiously added, until the blue tinge given to the a.r.s.enious acid test-liquor is destroyed; care being taken to stir the mixture well during the whole process, and to stop as soon as the decolorisation is completed.

Let us suppose now that, in order to destroy the blue colour of the 1000 grains measure of the a.r.s.enious acid test-liquor, 90 divisions or degrees of the chloride-of-lime solution have been employed. These 90 divisions, therefore, contained the 10 gr. of chlorine required to destroy the colour of the test-solution; and since each division represents 1/2 gr. of chloride of lime, 45 gr. of chloride of lime (10 gr. of chlorine) were present in the 90 divisions so employed, from which the per-centage strength may be ascertained. For--

45 : 10 : : 100 : 2222

The chloride of lime examined, therefore, contained 22-1/4 per cent, (nearly) of chlorine.

_Obs._ This method is extremely simple and trustworthy when properly employed; but to ensure accuracy, certain precautions must be adopted.

Instead of pouring the test-liquor into the solution of the sample (as in alkalimetry), the solution of the sample must be poured into the test-liquor.

Vogel found that in a normal solution of a.r.s.enious acid that had been prepared for using in the above process, half the quant.i.ty of the a.r.s.enious acid became oxidised to a.r.s.enic acid in the course of about a year. He therefore recommends that the standard solution, if kept for some time, should be tested by a magnesium salt. The formation of a precipitate would show the solution had undergone such a change, as to render it unfit for volumetric estimations.

_Penot's Process._ This is a modification of the previous process. For the a.r.s.enious acid solution a.r.s.enite of soda is subst.i.tuted, and for the indigo solution a colourless iodised paper, which is turned blue by the smallest quant.i.ty of free acid. The paper is prepared in the following manner:--1 gram of iodine, 7 grams of carbonate of soda, 3 grams of starch, and a quarter of a litre of water are mixed. When the solution becomes colourless it is diluted to half a litre; in this fluid, white paper is soaked. The a.r.s.enical fluid is prepared by dissolving 444 grams of a.r.s.enious acid, and 13 grams of crystallised carbonate of soda in 1 litre of water. This solution is added by means of a burette to the solution of chloride of lime intended to be tested (10 grams of the sample to 1 litre) the completion of the reaction being known by the paper remaining uncoloured.

Lunge says that the same piece of moist iodine test paper may be made use of repeatedly, since the spots produced by testing usually disappear after about twenty-four hours if exposed to the air. The paper must, however, be kept away from dust.

_Wagner's Process._ This method is based upon the fact that a solution of chloride of lime separates the iodine from a weak (1 to 10) and slightly acidified iodide-of-pota.s.sium solution, the iodine being quant.i.tatively estimated by means of hyposulphite of soda:--

Iodine 21, } {Iodine of sodium, 2NaI, Hyposulphite of } yield {Tetrathionate of sodium, Na_{2}S_{4}O_{6}, soda, 2Na_{1}SO_{3} } {Water, 5H_{2}O.

+5H_{2}O,

The test is performed as follows:--100 c. c. =1 gram of bleaching-powder solution, obtained by dissolving 10 grams of chloride of lime in 1 litre of water, are mixed with 25 c. c. of solution of iodide of pota.s.sium acidified with dilute hydrochloric acid. The resulting clear, deep brown-coloured solution is treated with hyposulphite of soda solution until quite colourless. The hyposulphite of soda solution is composed of 248 grams of that salt to 1 litre of water; 1 c. c. of this solution neutralises 00127 grams of iodine, and 000355 grams of chlorine.

_Otto's Process._ This method is based upon the following data. Two molecular weights of protosulphate of iron when brought into contact with chlorine, in presence of water, and free sulphuric acid, give one molecule of persulphate of iron, and two molecules of hydrochloric acid, the process consuming one molecule of chlorine. Two molecules of crystallised sulphate of iron = 556, correspond to 710 of chlorine, or in other terms 07839 grams of the crystallised sulphate correspond to 01 gram of chlorine.

_Bunsen's Process._ This consists in adding iodide of pota.s.sium to the bleaching-powder liquor, acidulating the mixture with hydrochloric acid, and running the solution of a.r.s.enite of soda into it till only a yellow tint shows itself. A little starch paste is now added, and the a.r.s.enite solution cautiously introduced drop by drop, till the blue colour just disappears. The solutions must all be standardised. To preserve the starch paste Mohr advises the addition to it of a little chloride of zinc.

_Mr Davies_ uses glycerin as a solvent for the a.r.s.enious acid. He prepares a standard solution as follows:--1395 grains of a.r.s.enious acid in 40 c.

c. of glycerin and fitted up to 1 litre. Every c. c. corresponds to 01 grain of chlorine. Indigo sulphate solution is used as an indicator, and the bleaching liquor is run into the glycerin solution until the blue colour of the latter is changed to a brownish yellow.

_Dr Ure's_ as follows:--Liquor of ammonia, of a known strength, tinged with litmus, is added to a solution of a given weight of the chloride under examination, until the whole of the chlorine is neutralised, which is known by the colour being destroyed. From the quant.i.ty of ammonia consumed the strength of the sample is estimated.

The value of bleaching powder is estimated in England, America, and Germany by degrees corresponding to the per-centage of available chlorine contained in a sample of chloride of lime by weight; but in France the degrees denote the number of litres of chlorine gas at 0 c. and 760 Mm.

Bar., which 1 kilo of bleaching powder can evolve. In the following table the chlorometrical degrees of France and England are contrasted:--

French. English.

63 2002 65 2065 70 2224 75 2383 80 2542 85 2701 90 2860 100 3180 105 3336 110 3495 115 3654 120 3813 125 3972 126 4004