Part 201
_Prop._ Tasteless; scentless; of an intense blue colour, passing into purple; when rubbed with a smooth hard body, it assumes a coppery hue; insoluble in water, cold alcohol, ether, alkalies, hydrochloric acid, dilute sulphuric acid, and the cold fixed and volatile oils; slightly soluble in boiling alcohol and oils; freely soluble in concentrated sulphuric acid, and, when decoloured or reduced by contact with deoxidising substances, in alkaline lyes; soluble in creasote; its colour is destroyed by chromic acid, nitric acid and chlorine; when suddenly heated, it gives off rich purple fumes, which condense into brilliant copper-coloured needles.
_Pur._ The best indigo is that which has the deepest purple colour, that assumes the brightest coppery hue when rubbed with the nail; its fracture is homogeneous, compact, fine-grained, and coppery; its powder is of an intensely deep blue tint, and light enough to swim on water; and it leaves only a fine streak when rubbed upon a piece of white paper. In general, when indigo is in hard, dry lumps of a dark colour, it is considered of bad or inferior quality. Indigo, when in hard or brittle lumps, or in dust or small bits, is often adulterated with sand, pulverised slate, and other earthy substances.
_Estimation._ Various methods for estimating the value of samples of indigo have been proposed, but none of them can be depended upon to give perfectly accurate results. The plan recommended by O'Neill[353] is perhaps the best; it is performed as follows:--
[Footnote 353: See 'Dictionary of Calico Printing and Dyeing.']
Weigh 25 gr. of a fair sample of the indigo finely ground; and to soften or disintegrate it still further, boil it for a short time with weak caustic soda, and then, if there be any soft lumps or clots, strain through calico; mix this with 3 quarts of water in a narrow-necked bottle which it will nearly fill, and add 400 gr. of quicklime, which has been slaked as perfectly as possible; shake well up and add a 1000 gr. measure of solution of green copperas (protosulphate of iron) at 30° Twaddell; cork the bottle closely, and leave it for three days, frequently shaking it in the interval. The indigo will be dissolved by this time; 1 quart of the clear solution is drawn off, shaken up in a bottle to oxidise it, acidified with acetic acid, and the pure indigo (INDIGOTIN) collected upon a filter, dried, and weighed. Four times the weight of the pure indigo is the per-centage of indigo in the sample.
_Uses._ As a dye stuff indigo is of great importance, both from the beauty and permanence of the colour it yields, and from the ease with which it is applied to fabrics of all materials. As a medicine it has been employed in various affections of a spasmodic character, as chorea, convulsions, epilepsy, hysteria, &c. In large quantities it often induces giddiness, vomiting, and diarrh[oe]a; and when continued for sometime, muscular twitchings, resembling those arising from strychnine.--_Dose._ Beginning at about 15 gr., and gradually increased to 1, 2, or even 3 dr., at which it should be continued for 3 or 4 months; made into an electuary with honey or sugar, to which some aromatic may be added. See INDIGO DYE, INDIGOTIN, &c.
=Indigo, Sul'phate of.= _Syn._ SULPHINDYLIC ACID, SULPHINDIGOTIC A., SAXONY BLUE, SOLUBLE INDIGO.
_Prep._ By gradually adding indigo (in fine powder), 1 part, to fuming sulphuric acid (Nordhausen sulphuric acid), 5 parts, or oil of vitriol, 8 parts contained in a stone-ware vessel placed in a tub of very cold water, to prevent the mixture heating; the ingredients are stirred together with a glass rod at short intervals until the solution is complete, after which the whole is allowed to repose for about 48 hours, by which time it becomes a homogeneous pasty mass of an intense blue colour, which in a dull light appears nearly black.
_Obs._ In this state it forms 'BARTH'S BLUE,' or the 'CHEMIC BLUE' or 'INDIGO COMPOSITION' of the dyer. Diluted with about twice its weight of soft water, it is converted into the 'SAXONY BLUE' or 'LIQUID BLUE' of the shops, also used for dyeing. When commercial sulphate of indigo is diffused through a large quantity of water, nearly boiling, and wool (old white flannel rags, &c.) is macerated in it for some time, the latter absorbs the whole of the sulphate and is dyed blue, whilst the liquor assumes a greenish-blue colour. Wool, so prepared, when well rinsed in cold water, and boiled for some minutes in a large quantity of that liquid containing 1% or 2% of carbonate of potassa, or a quantity equal to about 1-3rd that of the indigo originally employed, gives up its blue colour, and becomes of a dull brown. The liquid is now a rich blue-coloured solution of sulphindylate of potassa, from which the salt may be obtained by cautious evaporation. This compound is prepared on the large scale, by diluting sulphate of indigo with about 12 times its weight of soft water, and imperfectly saturating the solution with carbonate of potassa; the sulphindylate falls down as a dark-blue coppery-looking powder, soluble in 140 parts of cold water and in about 90 parts of boiling water. This substance is kept both in the moist and dry state, and is known in commerce under the respective names of 'DISTILLED INDIGO,' 'PRECIPITATED INDIGO,' 'SOLUBLE INDIGO,' 'INDIGO PASTE,' 'BLUE CARMINE,' 'DISTILLED BLUE,' 'SOLUBLE BLUE,' &c. It is extensively used in dyeing; and when mixed with starch, whilst in the moist state, and made into cakes or knobs, it constitutes the finest variety of the 'BLUE' used by laundresses for tinging linen. The ammonia and soda salts may be prepared in the same way as the potassa salt, by substituting the carbonates of those bases for carbonate of potassa. The ammonia salt is very soluble.
=INDIGO BLUE.= See INDIGOTIN.
=INDIGO DYE.= There are two methods of preparing solutions of indigo for dyeing.--1. By deoxidising it, and then dissolving it in alkaline menstrua.--2. By dissolving it in sulphuric acid. The former method is used in preparing the ordinary INDIGO VAT of the dyers.
1. _a._ (COLD VAT.) Take of indigo, in fine powder, 1 lb.; green copperas (clean cryst.), 2-1/2 to 3 lbs.; newly slaked lime, 3-1/2 to 4 lbs.; triturate the powdered indigo with a little water or an alkaline lye, then mix it with some hot water, add the lime, and again well mix, after which stir in the solution of copperas, and agitate the whole thoroughly at intervals for 24 hours. A little caustic potassa or soda is frequently added, and a corresponding portion of lime omitted. For use, a portion of this 'preparation vat' is ladled into the 'dyeing vat,' as wanted. After being employed for some time, the vat must be refreshed with a little more copperas and fresh-slaked lime, when the sediment must be well stirred up, and the whole thoroughly mixed together. This is the common vat for cotton.
_b._ (POTASH VAT.) Take indigo, in fine powder, 12 lbs.; madder, 8 lbs.; bran, 9 lbs.; 'potash,' 24 lbs.; water at 125° Fahr., 120 cubic feet; mix well; at the end of about 36 hours add 14 lbs. more potash, and after 10 or 12 hours longer further add 10 lbs. of potash, and rouse the whole up well; as soon as the fermentation and reduction of the indigo are well developed, which generally takes place in about 72 hours, add a little fresh-slaked lime. This vat dyes very quickly, and the goods lose less of their colour in alkaline and soapy solutions than when dyed in the common vat. It is well adapted for woollen goods.
_c._ (WOOD VAT.) As the last, but employing wood instead of madder; the vat is 'set' at 160° Fahr., and kept at that temperature until the deoxidation and solution of the indigo has commenced. The last two are also called the 'warm vat.'
_d._ (PASTEL VAT.) This is 'set' with a variety of wood which grows in France, and which is richer in colouring matter than the plant commonly known as 'wood.'
_e._ (SCHÜTZENBERGER and DE LALANDE'S VAT.) It is known that the low stage of oxidation of sulphur obtained on the reduction of sulphurous acid with zinc, dissolves indigo. On this reaction the following proceedings for dyeing and printing with indigo are founded:--To prepare the reducing liquid, a solution of bisulphite of soda at 35° B. is brought in contact with sheet zinc in a closed vessel, of which the liquid should occupy only one fourth. After the lapse of an hour the zinc is precipitated from the clear liquid by means of milk of lime. It is then diluted or decanted, or filtered with exclusion of air.
The clear liquid is then poured upon the ground indigo, with the addition of the needful soda and lime. One kilo of indigo yields in this manner a very concentrated vat of from 10 to 15 litres. Cotton is dyed cold, and wool with the aid of heat. A vat is filled with water, and a suitable quantity of the above indigo mixture introduced, when the dyeing can be performed at once. The excess of the low sulphur acid dissolves the froth which appears on the surface. During the process of dyeing, further quantities of indigo can be added as required. Cotton can be rapidly and easily dyed in this manner; and in the case of wool, the dyer escapes the many disadvantages of the hot vat and obtains brighter and clearer shades. To print a fast blue the alkaline solution of the reduced indigo is printed on with an excess of the reducing agent, aged for twelve to twenty-four hours, washed and soaped. In comparison with the old process there is a saving of indigo to the extent of 50 to 60 per cent.; the shades are richer and the impressions sharper. The colour requires no subsequent treatment, and can therefore be printed on simultaneously with most other colours.
_Obs._ Wool, silk, linen, and cotton, may each be dyed blue in the indigo vat. The goods, after being passed through a weak alkaline solution, are subjected to the action of the vat for about fifteen minutes; they are then freely exposed to the air; the immersion in the vat and the exposure are repeated until the colour becomes sufficiently deep. Wood and madder improve the richness of the dye. Other deoxidising substances, besides those above mentioned, may be used to effect the solution of the indigo; thus a mixture of caustic soda, grape sugar, indigo, and water, is often employed on the Continent for this purpose; and orpiment lime, and pearlash are also occasionally used. When properly prepared, the indigo vat may be kept in action for several months by the addition of one or other of its constituents, as required. An excess of either copperas or lime should be avoided.
2. Solution of sulphate of indigo is added to water, as required, and the goods, previously boiled with alum, are then immersed in it, and the boiling and immersion are repeated until the wool becomes sufficiently dyed.
_Obs._ With this every shade of blue may be dyed, but it is most commonly employed to give a ground to logwood blues. The colouring matter has affinity for woollen and silk with or without 'mordant,' but none for cotton. A solution of soluble indigo (sulphindylate of potassa or soda), in water very slightly acid with sulphuric acid, imparts a very fine blue to cloth, superior in tint to that given by the simple sulphate. See DYEING, &c.
=INDIGO PUR'PLE.= _Syn._ PH[OE]NICINE. The name given by Mr Crum to the purple precipitate obtained by filtration from a solution of indigo in fuming sulphuric acid, when largely diluted with water.
=INDIGO RED.= _Syn._ INDIGO RESIN, RED RESIN OF INDIGO. This is prepared by boiling alcohol (sp. gr. ·830), on powdered indigo previously exhausted by digestion in dilute acids and in a strong alkaline solution. When heated, it is converted into a white sublimate (deoxidised indigo red), but recovers its red colour by the action of nitric acid.
=INDIGO WHITE.= _Syn._ INDIGOGENE, INDICYLE, REDUCED INDIGO, HYDROGENISED I., HYDRATE OF I. Reduced or deoxidised indigo blue.
_Prep._ The yellow alkaline solution obtained by one or other of the processes noticed under INDIGOTIN is carefully protected from the air, both before and after precipitation with hydrochloric acid; and the precipitate, after being rapidly washed with recently boiled distilled water, or with very dilute sulphurous acid, is drained on a filter, dried in vacuo, and then at once transferred to a well-stoppered bottle.
_Prop., &c._ A greyish-white mass of minute crystals, generally light blue on the surface, and rapidly turning blue on exposure to the air; soluble in alkalies, alcohol, and ether, to which it imparts a yellow colour. These solutions deposit indigo blue on exposure to the air. A solution of this substance constitutes the indigo vat of the dyer (see _above_).
=INDIGO'TIN.= _Syn._ CERULIN, INDIGO BLUE. This is the pure blue principle of indigo. It appears to be the oxide of the same organic radical of which indigo white is probably the hydrate.
_Prep._ 1. Indigo (in fine powder) is digested successively in dilute hydrochloric acid, solution of potassa, and alcohol; the dried residuum is crude indigotin.
2. Indigo (in fine powder), 1 part; green sulphate of iron, 2 parts; hydrate of lime, 3 parts; water, 15 parts; mix, agitate occasionally until the colour is destroyed, then decant the clear portion, precipitate with dilute hydrochloric acid, and wash the powder first with water, and then with boiling alcohol, until the latter ceases to acquire a yellow colour.
3. Caustic soda and grape sugar, of each 1 part; water, 20 parts; powdered indigo, 5 parts; mix, and proceed as last. The above are essentially the same as the indigo vat, but on the small scale.
4. The process for estimating the value of indigo given under INDIGO is a good process for obtaining Indigotin.
_Obs._ The product from all the above exceeds 50% of the indigo operated on.
5. (Taylor.) Powdered indigo, 2 parts; plaster of Paris, 1 part; water, q. s. to reduce the mixture to a thin paste; spread the mass evenly upon an oblong iron plate to the depth of about 1/8 inch, and dry it by a gentle heat. It must then be held over the flame of a spirit lamp, when a disgusting odour will be evolved, the mass will begin to smoke, and in a few minutes will be covered with a heavy purple vapour, which will condense into brilliant flattened prisms or plates of an intense copper colour, forming a thick velvety coating over the surface immediately exposed to the heat. Should the mass catch fire, it may be instantly extinguished by a drop of water let fall upon it. _Prod._ 15 to 18%. See INDIGO, &c.
=INDIUM.= IN. = 113·4. This very rare metal was discovered by means of the spectroscope by Messrs Reich and Richter in a specimen of zinc-blende from Freiberg, in 1863. Since then it has been found in the flue dust of some zinc furnaces worked in the Hartz mountains, also in a black blende, known as christophite, occurring in Saxony; in the Wolfranc of Zinnwald, associated with zinc, as well as in Wolfranc alone; and also in the blende met within steatite, near Schlaggenwald. In all of these substances the indium is present in very minute quantity,[354] and is more or less associated with lead, arsenic, cadmium, iron, and copper; its separation from which is matter of no inconsiderable labour and difficulty.
[Footnote 354: In the flue dust of the zinc furnaces it is present to the amount of about 0·1 per cent.; in christophite in the proportion of 0·0062 per cent.]
The following process for the detection of indium in zinc-blende, and its extraction from the same source, is given by Winkler. Precipitate the hydrochloric acid solution of the roasted ore with metallic zinc at the boiling heat; dissolve the precipitate in nitro-hydrochloric acid; remove the arsenic, cadmium, &c., by sulphuretted hydrogen, and precipitate the indium as oxide by barium carbonate. Should this precipitate contain any iron, it must be removed by resolution, heating with sodium sulphate, and digestion with barium carbonate in a closed vessel. The indium may also be precipitated from the original solution, either directly by barium carbonate, or from a solution containing sulphuric acid, by neutralisation with sodium carbonate, till a precipitate begins to form, and addition of sodium acetate; it is then precipitated as a basic sulphate containing zinc."[355]
[Footnote 355: Various other processes are given in 'Watts' Dictionary.']
Indium may be obtained in the metallic state from the reduction of its oxide by means of hydrogen; charcoal or carbonaceous fluxes are not good reducing agents, as their employment necessitates a very high temperature, and loss from volatilisation occurs. Sodium is found to be the best reducing agent when large quantities of the metal are required.
Böttger's method is to precipitate the indium by zinc, to press the spongy metal so obtained in hot water, then to submit it to pressure in a screw press between filtering paper, and finally to melt it with cyanide of potassium.
_Prop._ Indium is a soft, white, durable metal, somewhat resembling cadmium, wholly destitute of crystalline structure. Its specific gravity, which is 7·421 at 16·8° C., is not altered by rolling or hammering. When heated in the air to 176° C., it melts without becoming oxidised; at a temperature above this, however, it becomes covered with a coating of suboxide, becoming gradually changed into the yellow sesquioxide. Indium is less volatile than either cadmium or zinc. It dissolves slowly in dilute sulphuric and hydrochloric acids, hydrogen being given off. In strong hydrochloric acid it dissolves rapidly. Nitric acid oxidises it, evolving at the same time nitric oxide; whilst sulphuric acid converts it into anhydrous sulphate.
When examined by means of the spectroscope, the flame of indium reveals two brilliant bands--a violet and a blue one.
Indium is completely precipitated from a solution of its acetate, as well as from neutral solutions of its salts in general, by sulphuretted hydrogen. Ammonia, neutral sodium carbonate, and acid sodium carbonate, throw down white precipitates insoluble in excess of the precipitant; caustic potash and soda produce a white precipitate of indium hydrate, soluble in excess. Barium carbonate precipitates it completely. Potassium ferrocyanide gives a white precipitate.
_Estim._ "The most convenient method of estimating indium is by precipitating it as hydrate with ammonia, dissolving the washed precipitate in hot dilute nitric acid, evaporating, igniting, and weighing the oxide thus obtained. Precipitation with sulphuretted hydrogen does not give exact results on account of the solubility of the indium sulphide."[356]
[Footnote 356: Watts.]
Indium forms compounds with bromine, chlorine, iodine, oxygen, and with several of the organic and inorganic acids.
=INDURA'TION.= In _pathology_, an increase in the consistence of any portion of the body, usually resulting from chronic inflammation, pressure, or friction.
=IN'FANCY.= "The domestic treatment of infants and children is comprised in the application of the laws of health to the mother as well as to the child. The position of parent is one of serious responsibility, both morally and physically, and the edict has gone forth that 'the sins of the parent shall be visited on the children.' If we could ensure good mothers, we could vastly improve the race of men. The nursing mother of a sick infant must, by following faithfully the rules of health in respect of the four great hygienic principles--food, clothing, exercise, and ablution--give health with her milk to her offspring; she must also pay close attention to her mind, avoid all sources of irritation and anxiety, and remember that an angry mother sours her milk, and produces a fractious and often a diseased infant. I am quite of opinion that if mothers were sound in constitution, and bestowed the requisite care upon the maintenance of their health, we should hear little of diseases of children. In children, as well as in parent, the rules of health must be carried out," and their neglect cannot fail to bring with it a heavy retribution. (Eras. Wilson.) See EXERCISE, NURSING, &c.
=INFANT DEATH-RATE.= In England, according to Dr Farr, out of 1000 infants born, 149 die annually before reaching their first year; and the same authority tells us that 311 out of every 1000 die during the first month in the same period. Amongst illegitimate children, the lives of one half never exceed the first month.
The above figures represent the yearly average of infantile deaths throughout the whole of England, when we come to the large cities the mortality is notably higher. In Liverpool, for instance, out of 1000 children born, 239 died in their first year.
When we examine into the infant mortality prevailing amongst different classes, we find the proportion existing between the death-rate of the children of the nobility, and the general death-rate up to one year, to be as 3 to 8.
In 1874, Mr Charles Ansell, jun., published a work entitled 'Statistics of Families of the Upper and Professional Classes,' in which he showed, from investigations into the deaths occurring amongst 48,000 children of the wealthy, professional, and titled classes, that in the first year of life, about 80 only of such children die out of every 1000. According to Dr Farr, the northern countries of Europe show a much lower infant death-rate than the southern ones. Infant mortality is lowest in Norway, and highest in High Bavaria, where 404 infants per 1000 die in their first year. In New York, in 1869, the mortality amongst infants under one year old was 27·4 per cent. and in 1873, 31·0 per cent.
Both in France and England the mortality prevailing amongst illegitimate children up to the age of one year is very large. In 1860, the death-rate amongst the foundlings of the Loire-Inférieure, was as much as 876 in the 1000, and it averages between 500 and 700 in France. In Wakefield, amongst the same class of children, it was 26·22 per cent.; in Coventry, 40; in Padstow, 50; and in Bantry, 80; in manufacturing towns the average is 35 per cent. In London the number of illegitimate children who die annually under the age of a year is probably about 75 per cent.[357]
[Footnote 357: 'Proceedings of the Obstetrical Society for 1870.']
In the Montreal Foundling Asylum, out of 4060 infants, only 7 per cent. lived one year. In the rural districts of England and also in Bavaria, the average of deaths at one year is about the same for the illegitimate as for the legitimate children.
In the 'Transactions of the Obstetrical Society for 1870' there is a valuable and interesting report, throwing much light on the condition and treatment of the children of the poor in England. The following is the substance of this report, the information contained in which was collected by various members of the society:--It was found that amongst the poorer populations of villages 30 to 90 per cent. are attended by midwives, and that this custom prevails to an almost equal extent in the large provincial and manufacturing towns. Thus in Glasgow, 75 per cent., in Coventry, 90 per cent.; and in Leeds and Sheffield, equally large numbers of the population employ the services of these women. In Edinburgh the midwife is rarely called on; neither is she in the West End of London; but in the East End 30 to 50 per cent. of the accouchements are undertaken by women.