Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 108

There are four chlorides of osmium, the best known of which are the dichloride and the tetrachloride.

1. =Osmium dichloride.= (OsCl_{2}). _Syn._ OSMIOUS DICHLORIDE, OSMIUM PROTOCHLORIDE. This is green, and sublimes in green needles. It may be obtained by heating metallic osmium in a current of dry chlorine gas. It forms double salts, which are of a green colour.

2. =Osmium tetrachloride.= (OsCl_{4}). _Syn._ OSMIC TETRACHLORIDE, OSMIUM BICHLORIDE. This may be procured in the same manner as the dichloride, using, however, an excess of chlorine. It occurs as a red, crystalline, fusible, deliquescent powder. It is more volatile than the dichloride.

Both the dry chloride and the tetrachloride of osmium are dissolved by water, which decomposes them into tetroxide of osmium, hydrochloric acid and the metal.

=OSTEOCOL'LA.= A rough sort of glue or gelatin obtained from bones by digestion in dilute hydrochloric acid, to remove their earthy matter, and afterwards acting on the residuum with water at a high temperature, until it is wholly dissolved.

=OTAL'GIA.= Pain in the ear. See EARACHE.

=O"THYL.= In chemistry, a radicle having the formula C_{2}H_{3}O, a.s.sumed by Professor Williamson to exist in acetic acid.

=OT'TO OF ROSES.= See OILS (Volatile).

=OVALBU'MEN.= White of egg; to distinguish it from seralb.u.men, or the alb.u.men of the serum of the blood.

=O'VENS.= A very ingenious and useful improvement in the apparatus for baking was introduced some years ago by Mr Sclater, of Carlisle. It consists in causing the articles to be baked to traverse a heated earthenware tube. This tube forms the oven. It is of considerable length, and the biscuits or other articles are slowly traversed through it, from end to end, at such a rate as will allow of the baking being completed during the pa.s.sage. The biscuits are carried on trays, set on travelling chains; or the trays are made into an endless web or chain. The oven is thus entirely self-acting, and the articles demand no attention whatever from the attendants, whilst the system combines superior economy with the best results. A 'pyrometer,' or heat indicator, is attached externally, so that the attendant can regulate the heat with great facility. The object of these improvements is to reduce the cost of baking, and to improve the appearance of the baked articles. The apparatus is applicable as well to the baking of articles of clay or earthenware as to bread or biscuits.

Of the ovens now in common use by the bakers, that known as the 'hot-water oven' is perhaps the best; not merely in reference to economy, but also with reference to its superior cleanliness, and the ease with which the articles operated on may be turned out of that delicate yellowish-brown tint for which the bread of the Viennese and Parisian bakers is so celebrated. See BAKING, BREAD, &c.

=OWNER.= For the purposes of the Public Health Act this term is thus defined:--"'Owner' means the person for the time being receiving the rack-rent of the lands or premises in connection with which the word is used, whether on his own account, or as agent or trustee for any other person, or who would so receive the same if such lands or premises were let at a rack-rent."

=OX.= The _Bos Taurus_ (Linn.), one of the ruminantia. In its more limited sense the word is restricted to the emasculated animal. The flesh, milk, skin, horns, bones, and blood of this animal are all serviceable to man.

Goldbeater's skin is prepared from the peritoneal membrane of its caec.u.m.

Its blood, fat, horns, and excrement were among the simples of the Ph. L.

1618. See BEEF, GALL, MILK, and _below_.

=Ox-Gall.= Syn. OX-BILE; FEL BOVINUM, F. BOVIS, F. TAURI, L. Crude ox-gall is noticed at page 774. Refined ox-gall (_Fel bovinum purificatum_) is prepared as under:--

1. Fresh ox-gall is allowed to repose for 12 or 15 hours, after which the clear portion is decanted, and evaporated to the consistence of a thick syrup by the heat of a water bath; it is then spread thinly on a dish, and exposed in a warm situation near the fire, or to a current of dry air, until nearly dry; it is, lastly, put into wide-mouthed bottles or pots, and carefully tied over with bladder. In this state it will keep for years in a cool situation. For use a little is dissolved in water.

2. Fresh gall, 1 pint; boil, skim, add powdered alum, 1 oz.; boil again till the alum is dissolved, and when sufficiently cool pour it into a bottle, and loosely cork it down. In a similar manner boil and skim another pint of gall, add to it 1 oz. of common salt, and again boil, cool, and bottle it, as above. In three months decant the clear from both bottles, and mix them in equal quant.i.ties; the clear portion must then be separated from the coagulum by subsidence or filtration.

_Uses, &c._ Both the above are employed by artists to fix chalk and pencil drawings before tinting them, and to remove the greasiness from ivory, tracing paper, &c. The first is also used in medicine.

=OX'ALATE.= _Syn._ OXALAS, L. A salt of oxalic acid. The soluble oxalates are easily formed by directly neutralising a solution of oxalic acid with a metallic hydrate, carbonate, or oxide; and the insoluble oxalates, by double decomposition. See OXALIC ACID and the respective bases.

=OXAL'IC ACID.= H_{2}C_{2}O_{4}. _Syn._ ACIDUM OXALIc.u.m, L. This substance was discovered by Bergman in 1776. It occurs both in the mineral and organic kingdoms, and is produced artificially by the action of nitric acid on sugar, starch, woody fibre, &c. It abounds in wood-sorrel, in which it exists in combination with a little pota.s.sa. With the exception of gum and sugar of milk all starchy and saccharine substances yield oxalic acid when treated with nitric acid at a somewhat elevated temperature.

_Prep._ 1. From sugar:--

_a._ Nitric acid (sp. gr. 142), 5 parts, diluted with water, 10 parts, is poured on sugar, 1 part, and the mixture is digested at a gentle heat as long as gaseous products are evolved; the liquid is then concentrated by evaporation until it deposits crystals on cooling; the crystals, after being drained and freed from superfluous moisture, are redissolved in the smallest possible quant.i.ty of boiling water, and the solution is set aside to crystallise. The residuary 'mother-water' is treated with a little fresh nitric acid (say 1-1/2 part) at a gentle heat, after which it is evaporated, as before, for a second crop of crystals. This process is repeated until the solution is exhausted. The brownish-coloured crystals thus obtained are allowed to effloresce by exposure to dry air, and are then redissolved and recrystallised. By repeating this treatment they yield pure colourless oxalic acid at the third crystallisation.

_b._ (Schlesinger.) Sugar (dried at 257 Fahr.), 4 parts, and nitric acid (sp. gr. 138), 33 parts, are digested together, as before, and as soon as the evolution of gas ceases the liquid is boiled down to one sixth of its original volume, and set aside to crystallise. The whole process may be completed in about 2 hours, and in 1 vessel, and yields of beautifully crystallised oxalic acid, at the first crystallisation, a quant.i.ty equal to 56 to 60% of the weight of the sugar employed.

_c._ (Ure.) Nitric acid (sp. gr. 14), 4 parts, and sugar 1 part, are digested together by the heat of a water bath, and as soon as gas ceases to be extricated the vessel is removed from the heat, and set aside to cool and crystallise. The use of a little sulphuric acid along with the nitric acid contributes to increase the product.

2. From POTATO- or DEXTRIN-SUGAR:--(Nyren.) From the washed pulp of potatoes, boiled for some hours with water, q. s., in a leaden vessel, with about 2% of oil of vitriol, until the fecula of the pulp is converted into saccharine matter, shown by the liquid being no longer turned blue by iodine; the whole is then filtered through horse-hair bags or strainers, and the filtrate is evaporated until its density is such that a gallon of it weighs 14 to 14-1/2 lbs.; in this state it is converted into oxalic acid by treatment with nitric acid in the way already described. A similar process was patented some years ago by Messrs Davy, Macmurdo, and Co.

3. From SAWDUST:--(Roberts, Dale, & Co. Patent.) This process is the one now usually employed for the manufacture of oxalic acid on the large scale. It is based on Gay-Lussac's discovery, that wood and similar substances are converted into oxalic acid by fusion with caustic alkali.

The practical details of the process are thus given by Dr Murray Thomson, of Edinburgh:--(1) Hydrate of sodium and hydrate of pota.s.sium, mixed in the proportion of 2 equivalents of the former to 1 equivalent of the latter, are dissolved, and solution evaporated until of specific gravity 135; sawdust is now stirred in until a thick paste results. (2) This paste is then heated on iron plates, during which it is constantly stirred; water is first given off; the ma.s.s then swells; inflammable gases, hydrogen and carburetted hydrogen, are evolved, along with a peculiar aromatic odour. When the temperature has been maintained at 400 for one or two hours, this stage of the process is complete; the ma.s.s has now a dark colour, and contains only 1 to 4 per cent. of oxalic acid, and about 5 per cent. of formic acid. The bulk, therefore, of the ma.s.s at this stage consists of a substance whose nature is not yet known, but which is intermediate between the cellulose and oxalic acid. (3) The next stage consists in a simple extension of the last, in which the ma.s.s is heated till quite dry, care being taken that no charring takes place. It now contains the maximum quant.i.ty of oxalic acid, 28 to 30 per cent. (4.) This oxalic acid now exists as oxalate of pota.s.sium and sodium in the grey powder resulting from stage 3. This powder is now washed on a filter with solution of carbonate of sodium, which seems to have the singular and unexpected power of decomposing the oxalate of pota.s.sium and converting it into oxalate of sodium. At all events, it is quite true that all traces of pota.s.sa are washed out with the solution of carbonate of sodium. The only explanation that occurs to account for this unusual decomposition is that oxalate of sodium is a more insoluble salt than oxalate of pota.s.sium, and therefore may be formed by preference. (5) This oxalate of sodium is now decomposed by boiling milk of lime. Oxalate of calcium falls as a precipitate, and soda remains in solution. This soda is boiled down, and again made use of with fresh sawdust. This recovery of alkali is also practised with the pota.s.sium salt which filters through in the last stage.

(6) The oxalate of calcium is now decomposed in leaden vessels with sulphuric acid. Sulphate of calcium is precipitated, and oxalic acid is in solution, which is now evaporated, and the acid separates in crystals, which now need only to be recrystallised to make them quite pure, and fit the acid for all the purposes for which it is employed. _Prod._ By this ingenious process 2 lbs. of sawdust are made to yield 1 lb. of oxalic acid.

_Prop., &c._ Colourless, transparent, prismatic crystals, possessing a powerful sour taste and acid reaction; these effloresce in warm dry air, with loss of 28% (2 eq.) of water, and then form a white powder, which may be sublimed in part, without decomposition; the crystals are soluble in 8 parts of water (9 parts, "and form a solution of sp. gr. 1045,"--Ure) at 60 Fahr., in their own weight or less of boiling water, and in about 4 parts of alcohol; with the acids, it forms salts called oxalates.

_Tests._--1. Solution of chloride of barium occasions a white precipitate in neutral solutions of oxalic acid (oxalates), which is soluble in both nitric and hydrochloric acid.--2. Solution of nitrate of silver, under like circ.u.mstances, gives a white precipitate, which is soluble in nitric acid, and in ammonia, and which, when heated to redness, yields pure silver.--3. Lime water and solutions of all the soluble salts of calcium produce white precipitates, even in highly dilute solutions of oxalic acid or of the oxalates, which is freely soluble in both nitric and hydrochloric acid, but is nearly insoluble in either acetic or oxalic acid, and is converted into carbonate of calcium upon ignition.--4. Oxalic acid (or an oxalate), when heated, in the dry state, with oil of vitriol in excess, is converted into carbonate anhydride and carbonic oxide; the former produces a white precipitate with lime water, and the latter, when kindled, burns with a faint blue flame. Of the above tests, solution of sulphate of calcium (_vide_ No. 3) is the most delicate and characteristic.--5. It is distinguished from Epsom salt by its acid reaction, its solubility in rectified spirit, its complete dissipation by heat, and by emitting a slight crackling noise during its solution in water. See MAGNESIA (Sulphate).

_Uses, Pois., &c._ Oxalic acid is chiefly used in the arts of calico printing and bleaching; to remove ink-spots and iron moulds from linen, and to clean boot-tops. It is extremely poisonous. The treatment, in cases of its having been swallowed, is to promote vomiting, and to administer chalk, whiting, or magnesia, mixed up with water, in considerable quant.i.ties. The use of the alkalies or their carbonates must be avoided, as the compounds which these form with oxalic acid are nearly as poisonous as the acid itself. The remaining treatment is noticed under ACIDS. In poisoning by oxalic acid the nervous system is almost always affected, and the patients experience numbness, formication of the extremities, and sometimes convulsions, so that the symptoms somewhat approach those produced by strychnia, from which it is distinguished by its corrosive action on the tissues, and its effect upon the heart and circulatory system.

_Concluding Remarks._ The manufacture of oxalic acid is an important one.

The process of Roberts, Dale, and Co. has so much cheapened the price of oxalic acid, that in 1851 it sold for 16d. per lb., and in 1864 it only cost from 8d. to 9d. per lb. More than half the amount of oxalic acid used all over the world is now made from sawdust. In manufacturing the acid from sugar, on the large scale, the first part of the process is either conducted in salt-glazed stoneware pipkins of the capacity of 3 to 5 quarts each (which are about two thirds filled and set in a water bath), or in wooden troughs lined with lead, and heated by means of a coil of steam-pipe. On the small scale, a gla.s.s retort or capsule is commonly employed. The most appropriate temperature appears to be about 125 Fahr.

and the best evidence of the satisfactory progress of the decomposition is the free but not violent evolution of gas, without the appearance of dense red fumes, or, at all events, any marked quant.i.ty of them. When these are disengaged with violence and rapidity, a greater quant.i.ty of the newly formed acid suffers decomposition, and flies off in a gaseous form. The sp. gr. of the nitric acid commonly used on the large scale ranges from 122 to 127 equivalent quant.i.ties being taken. The evaporation is preferably conducted by the heat of steam. The evolved nitrous vapours are usually allowed to escape, but this loss may be in part avoided by conveying them into a chamber filled with cold damp air, and containing a little water, when they will absorb oxygen, and be recondensed into fuming nitric acid. Various modifications of this plan have been patented. That of Messrs McDougall and Rawson, which is one of the simplest and best, consists in pa.s.sing the mixed nitrous fumes through a series of vessels containing water, and connected together by tubes, so that the fumes which collect at the top of one vessel are conveyed to nearly the bottom of the next one, and then, bubbling up through the water, mix with the air, a supply of which is provided for the purpose. The nitrous fumes are thus brought alternately into contact with air and water, and by the time they reach the last vessel are reconverted into nitric acid. Another plan is to pa.s.s the mixed nitrous vapours through a vessel stuffed with some porous substance, as pumice-stone or pounded gla.s.s, conjointly with a supply of steam from a boiler and a supply of oxygen by a blowing machine.

The product obtained by skilful manipulation are--from good dry sugar, 128%; from good treacle, 107%.--"One cwt. of good treacle will yield about 116 lbs. of marketable oxalic acid, and the same weight of good brown sugar may be calculated to produce about 140 lbs. of acid." "As a general rule, 5 cwt. of saltpetre, or an equivalent of nitrate of soda, with 2-1/2 cwt. of sulphuric acid, will generate sufficient nitric acid to decompose 1 cwt. of good sugar, and yield, as above, 140 lbs. of fair marketable oxalic acid, free from superfluous moisture." (Ure.) On the small scale, 5 parts of sugar yield nearly 6 parts of crystallised acid.

Chemically pure oxalic acid is best prepared by precipitating a solution of binoxalate of pota.s.sium with a solution of acetate of lead, washing the precipitate with water, decomposing it, whilst still moist, with dilute sulphuric acid or sulphuretted hydrogen, and gently evaporating the filtrate so that crystals may form as it cools.

=OXALURIA.= Also known as the oxalic-acid diathesis; is an abnormal condition of the system, marked by the presence in the urine of crystals of oxalate of lime. The crystals occur as minute transparent octahedra, and sometimes in the form of dumb-bells. They can be easily recognised under a microscope with a power of from 200 to 250 diameters, when they present a very beautiful appearance. They differ from phosphatic deposits in being insoluble in acetic acid. Their presence is mostly indicated by the appearance in the urine of a cloud of mucus, which forms after the urine has stood some little time.

Oxaluria most generally affects persons of dyspeptic and sedentary habits and of nervous temperament; those suffering from skin affections and neuralgia are also occasionally attacked by it. In ordinary cases the treatment consists in the administration of the nitro-hydrochloric acid, in infusion of gentian two or three times a day, or of a course of quinine and iron, aided by plenty of exercise in the open air, care being taken to avoid fatigue. If it can be borne the shower bath should also be had recourse to. Rhubarb tarts and tomatoes, which contain oxalic acid, must be excluded from the diet; so also should aerated water and too much sugar.

If after a short time the oxalates should not disappear from the urine under this treatment, the patient should seek proper medical advice; since the persistent presence of this deposit is of very serious significance, as indicating the existence in the bladder of that dangerous form of urinary concretion known as 'mulberry calculus.'

=OXIDA'TION.= _Syn._ OXYDATION. The combination of bodies with oxygen, forming oxides; the operation or process adopted to induce or facilitate such conversion.

=OX'IDE.= _Syn._ OXYD; OXYDUM, L. A compound formed by the union of oxygen with another body.

=OXYCHLO"RIDE.= _Syn._ OXICHLORIDE; OXYCHLORIDUM, L. A term often loosely applied to compounds of an oxide and chloride, whether in definite or variable proportions. See ANTIMONY (Oxychloride), &c.

=OX'YCRATE.= _Syn._ OXYCRATUM, L. The old name of a mixture of vinegar and water, dulcified with honey.

=OXYCRO'CEUM.= See PLASTERS.

=OX'YGEN.= O. _Syn._ OXYGEN GAS, DEPHLOGISTICATED AIR, EMPYREAL A., VITAL A.; OXYGENIUM, L. An elementary body discovered by Scheele and Priestly in 1774. It is remarkable that, although this substance forms a large proportion of our atmosphere (nearly one fourth), and confers upon it the power of supporting respiration and combustion, and also const.i.tutes the princ.i.p.al portion of the water of our rivers and seas (eight ninths), and enters largely into the composition of the majority of the various mineral bodies that form the bulk of our globe, its existence should have remained unsuspected, or at least undetermined, until a comparatively recent date.

Oxygen is an essential const.i.tuent of all living organisms. It is absorbed by animals during respiration, and evolved in a free state by growing vegetables when exposed to sunlight. The oxygen gas of the atmosphere is mechanically mixed, not chemically combined, with the nitrogen.

_Prep._ 1. From red oxide of mercury, heated over a spirit lamp or a few pieces of ignited charcoal. The operation is usually performed in a small green-gla.s.s retort, or in a short tube of hard Bohemian gla.s.s, closed with a perforated cork furnished with a piece of bent gla.s.s tube of small bore, to convey the liberated gas to the vessel arranged to receive it. Pure. 1 oz. yields about 100 cubic inches.

2. From chlorate of pota.s.sium, as the last. Pure. 100 gr. yield nearly 100 cubic inches (Brande; 115--Ure). This is the plan adopted in the P. Cod.

The decomposition occurs with both the above substances at a heat below that of redness.

3. From a mixture of chlorate of pota.s.sium (in coa.r.s.e powder), 3 parts; powdered binoxide of manganese, 1 part; both by volume. Pure. 100 gr. of the mixture yield about 110 cubic inches as oxygen. This method, which has received the approval of Faraday, is exceedingly convenient. The gas is evolved with a rapidity which is entirely at the command of the operator by simply increasing or lessening the heat. The residuum in the retort may be kept for another operation, if not exhausted; or it may be at once washed out with a little warm water, and the manganese, which is uninjured by the process, reserved for future use. Red lead, black oxide of copper, red oxide of iron, and several other substances, answers nearly as well as binoxide of manganese.

4. From a mixture of bichromate of pota.s.sium, 3 parts; oil of vitriol, 4 parts; gently heated, as before. Yields pure oxygen very freely, and with a rapidity entirely at the will of the operator. (Balmain.)

5. From binoxide of manganese and oil of vitriol, equal parts; as the last. 44 gr. of pure binoxide of manganese yield 8 gr., or 24 cubic inches, of oxygen; 1 oz. yields 88 gr., or 256 cubic inches. (Liebig.)

6. (On the large scale.)--_a._ From nitre exposed to a dull red heat in an iron retort, or gun-barrel. 1 lb. yields about 1200 cubic inches of gas, contaminated, more or less, with nitrogen. (Ure.)