Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 107

[Ill.u.s.tration]

[Ill.u.s.tration]

[Ill.u.s.tration]

[Ill.u.s.tration]

The 'combustion tube' with its 'charge' is next placed in a 'furnace' or 'chauffer' of thin sheet iron (see middle figure _above_). Its open end is then connected with a 'drying tube' filled with fragments of fused chloride of calcium, and carefully weighed. This tube is, in its turn, connected with a small gla.s.s ('Liebig's potash bulbs') containing solution of pure pota.s.sa of sp. gr. 127, also carefully weighed. The junction with the first is made by means of a perforated cork; that with the second by means of a small tube of india rubber tied with silk, the whole being made quite air-tight. The apparatus is then tested by sucking a few bubbles through the liquid with the dry lips, when, if the level of the solution of pota.s.sa in the two legs continues unequal for some minutes, the joints are regarded as perfect. The whole arrangement being complete (see _engr._), burning charcoal is now placed in the furnace around the front part of the combustion tube, and when this has become red-hot the screen is slowly moved back, and more burning charcoal is added, until the furthest extremity of the tube has been exposed to its action. (Gas, burned in furnaces specially contrived for the purpose, is now usually employed instead of charcoal.) The firing is so regulated that the gas enters the pota.s.sa apparatus in bubbles easily counted, without any violence or inconvenience, and it is kept up as long as gas is extricated.

As soon as the apparatus is complete, and the slightest retrograde action is observed, the charcoal is removed from the combustion tube, and the extreme point of this last is broken off. A little air is then sucked through the apparatus in order to seize on any remaining carbonic-acid gas and moisture. The potash apparatus and the chloride of calcium tube are, lastly, detached, and again accurately weighed. The increase in the weight of the first gives the weight of the carbonic acid formed during the combustion; that of the second the weight of the water. The numbers equivalent to any given number of grains, found as above, are converted into the proportions per cent. by simply dividing them by the weight of the organic substance which has been employed in the experiment, and moving the decimal point of the result two figures to the right.

Gr. Gr.

1 gr. of _Carbonic acid_ = 027273 of _Carbon_ + 072727 of _Oxygen_, 1 " _Water_ = 011112 " _Hydrogen_ + 088888 "

-- -------- -------- 2 less 038385 equal to 161615 "

_b._ In applying the preceding method to volatile liquids, it is necessary to enclose them in a small bulb with a narrow neck, instead of mixing them directly with the protoxide of copper. The bulb with its contents is introduced into the combustion tube, and after some 6 or 8 inches of the protoxide is heated to redness, a hot coal is applied near where the bulb is situated, so that the liquid which it contains may be slowly volatilised and pa.s.sed through the heated ma.s.s in the state of vapour, and be thus completely burned. For further information, consult Fresenius'

'Chemical a.n.a.lysis.'

2. _Estimation of the_ NITROGEN--_a._ Several methods are employed for this purpose, but the only one of general application, and adapted to the non-scientific operator, is that of MM. Varrentrap and Will, described under GUANO. To ensure correct results, the caustic soda must be pure, and the lime of good quality and well burnt. The last, having been properly slaked with a little water, holding the former in solution, the mixture is thoroughly dried in an iron vessel, and then heated to full redness in an earthen crucible. The ignited ma.s.s is rubbed to powder in a warm dry mortar, and either used at once or carefully preserved from the air. The best quant.i.ty of the organic substance to operate on is, in this case, about 10 gr., which must be dried, and accurately weighed with the usual precautions. Bodies very rich in either nitrogen or hydrogen are best mixed with about an equal weight of pure sugar before triturating them with the soda-lime. MM. Varrentrap and Will weigh the nitrogen under the form of double chloride of platinum and ammonium, dried at 212 Fahr. This salt contains 6272% of nitrogen.

_b._ M. Peligot has modified the preceding plan by conducting the gaseous matter extricated during the operation into a three-bulb tube charged with a standard solution of sulphuric acid. This he subsequently pours into a beaker-gla.s.s, and after tinging it with a single drop of tincture of litmus, he tests it with either a standard aqueous solution of soda or one of lime in sweetened water, after the common method of alkalimetry. The difference between the saturating power of the acid in its normal condition and after its exposure in the condenser indicates the amount of ammonia formed. (See GUANO.) Each grain of ammonia contains 82353 gr. of nitrogen.

_Concluding Remarks._ The successful application of the above processes requires considerable care and some apt.i.tude in manipulating, as well as the employment of a very delicate balance for determining the weights. A greater error in the weighings than the 1/250 gr. cannot be tolerated when exact results are desired. The method of MM. Varrentrap and Will for the determination of nitrogen answers admirably for all organic compounds containing it, except those in which it exists under the form of hyponitrous, nitrous, and nitric acids; for which, however, it is not required. When extreme accuracy is aimed at, the atmospheric air in the apparatus, and that absorbed during the preliminary operations by the substances employed, must be expelled before the application of heat to the combustion tube. (See WATER, a.n.a.lYSIS OF.)

=OR-MOLU'.= [Fr.] This name is given to gold-coloured bra.s.s or bronze, so finished off as to have the appearance of gold, or of being gilt; but it is often applied in a more general sense. The French more particularly excel in working in or-molu, and the products of this branch of their industry hold an important position in the art manufactures of France.

To give or-molu its richest appearance, "it is not unfrequently brightened up after 'dipping' (that is, cleaning in acid) by means of a scratch-brush (a brush made of very fine bra.s.s wire), the action of which helps to produce a very brilliant gold-like surface. It is protected from tarnish by the application of lacquer." (Ure.)

Ure says or-molu contains more copper and less zinc than ordinary bra.s.s, and that although, in many of its applications, the colour is heightened by means of a gold lacquer, in some cases the true colour of the alloy is best preserved after it has been properly developed by means of dilute sulphuric acid.

=ORMSKIRK MEDICINE.= A nostrum supposed to prevent hydrophobia, so named after the residence of its inventor, Mr Hill, of Ormskirk. It is said to have consisted of the ingredients named below, but nothing certain is known on the subject, as the inventor died without revealing its secret:--Chalk, 1/2 oz.; Armenian bole, 3 dr.; elecampane root, 1 dr.; alum, 10 gr.; oil of aniseed, 5 or 6 drops; all in fine powder. For a dose, to be taken for 6 successive mornings, in a gla.s.s of weak milk and water.

=OR'PIMENT.= Native yellow sulphide of a.r.s.enic. The finest samples used by artists (golden orpiment) come from Persia. See a.r.s.eNIC (Tersulphuret).

=OR'RIS.= _Syn_. ORRIS ROOT, FLORENTINE R.; RADIX IRIDIS, L. The dried rhizome of _Iris Florentina_, _pallida_, and _Germanica_. Sialogogue, irritant, subacrid, and errhine. Chiefly employed to impart a violet odour to oils, tooth powder, snuffs, spirits, &c.; and when cut into peas to keep open issues.

=ORSE'DEW.= Dutch leaf-gold.

=ORSEL'LIC ACID.= Two compounds pa.s.s under this name--ALPHA-ORSELLIC ACID and BETA-ORSELLIC ACID. They closely resemble each other, and are obtained in a similar manner; the first from the South American variety of _Rocella tinctoria_, the last from that grown at the Cape.

=ORSELLIN'IC ACID.= _Syn_. LECANORIC ACID. A compound formed along with picroerythrine, by boiling erythric acid for some time with water. It is also formed by boiling alpha-orsellic acid with water. In both cases, if the ebullition is too long continued, the new acid is wholly or in part converted into orcin.

_Prop., &c._ Crystallisable; bitter-tasted; soluble in water; its aqueous solution, by exposure to the air, a.s.sumes a beautiful purple colour.

=ORTHOCLASE.= _Syn._ POTa.s.sIUM FELSPAR. This material, which is a double silicate of pota.s.sium and aluminium, enters into the composition of many rocks, and is a common ingredient in granite. It has the following composition:--Silica, 648 parts; alumina, 184 parts; and potash, 168 parts. Part of the pota.s.sium is frequently replaced by small quant.i.ties of calcium, magnesium, and sodium.

Orthoclase is used for glazing the finest varieties of porcelain, a very intense heat being necessary to effect its fusion in the porcelain furnace. By the Chinese potters it is called _petuntze_. "The name 'orthoclase' is generally restricted to the subtranslucent varieties, there being many subvarieties (founded on variations of l.u.s.tre, colour, and other differences), of which the following are some of the princ.i.p.al, viz. _adularia_, a transparent or translucent felspar, met with in granitic rocks (frequently in large crystals); _moonstone_; _sunstone_; _Murchisonite_, _erythrite_; gla.s.sy felspar or _lanadine_, a transparent variety found in volcanic rocks, containing 4 per cent. of soda or upwards."[79]

[Footnote 79: Ure.]

=ORTHOPae'DIA.= In _surgery_, the straightening, correcting, or curing deformities of children. See SURGERY.

=OSIER.= The osier, which is a species of willow (_salix_), and is largely used in the construction of baskets and other wickerwork, is extensively cultivated at Nottingham and on the level lands of Cambridges.h.i.+re and Huntingdons.h.i.+re, as well as on the banks of the Thames, Severn, and other rivers. The small islands in these rivers, when planted with osiers, are known as osier HOLTS. But large as is the supply of shoots afforded by the English osier beds, it is insufficient for home consumption; hence great quant.i.ties of ozier rods are imported into this country from Holland, Belgium, and France. There are a great variety of oziers, and it is found that those which have been the most highly cultivated yield the toughest and finest wood, and those best adapted for the superior kinds of basket work. The branches of the wilder and less domesticated kind, which are more liable to break, are used for making hoops and coa.r.s.e baskets. This last variety, which is known as the COMMON OSIER (_Salix viminalis_), grows on the alluvial grounds of Britain, and in other European countries, and is often planted on the banks of rivers to prevent their being washed away.

The following are the princ.i.p.al varieties of osier indigenous to this country, and which yield the most valuable wood:--1. THE FINE BASKET OSIER (_Salix Forbyana_). 2. THE GREEN-LEAVED OSIER, or ORNARD (_Salix rubra_).

3. THE SPANISH ROD (_Salix triandra_). 4. THE GOLDEN OSIER, or GOLDEN WILLOW (_Salix vitellina_).

The osier requires plenty of water, and hence it thrives best in those localities and low grounds which are washed by a river. The soil best adapted for it is a rich but not clayey one. In planting an osier bed an important condition is that the trees should be placed sufficiently closely together, since it is found that, with too much s.p.a.ce, the shoots do not develop into long and slender branches, which are so much sought after. The shoots are cut once a year, at any time between the fall of the leaf and the rising of the sap in spring. After being cut they are divided into those destined for brown, and those for white baskets. In the latter ease the rods have to be peeled, but as this operation cannot be performed at once, and the rimous of the bark would be difficult were they allowed to dry, the shoots are placed upright and sustained in that position in wide shallow trenches in about four inches of water, where they are kept until they begin to bud and blossom in the spring, which they do as if they were attached to the parent plant. The peeling is easily done by pa.s.sing them through an instrument known as a _break_. If the spring has been a cold one, they have, previous to peeling, to be laid for some time under a layer of litter.

When they have been peeled they are stacked, preparatory to being sold.

With the rods intended for brown baskets, no peeling is of course necessary. They are therefore carefully stacked in some place protected from the rain, and diligently watched to see that no heat is set up in them, as is sometimes the case with freshly stacked hay, and which, if not stacked, would cause the rods to rot and render them useless.

In England, besides the native produce, 5000 tons of osiers are annually imported, valued at about 40,000. Of late years the Australian colonists have turned their attention to the cultivation of the osier, in the hopes of supplying the demand for it in Great Britain.

=OS'MAZOME.= The substance on which the peculiar odour and flavour of boiled meat and broth were formerly supposed to depend.

_Prep._ From lean meat, minced, and digested in cold water, with occasional pressure; the filtered infusion is gently evaporated nearly to dryness, and then treated with alcohol; the alcoholic tincture is, lastly, evaporated. The product has a brownish-yellow colour, is soluble in water, and its aqueous solution is precipitated by infusion of galls and the mineral astringent salts.

=OS'MIUM.= Os. A rare metal found a.s.sociated with the ores of platinum by M. Tennant, in 1803.

These ores mostly consist of a mixture of platinum, palladium, rhodium, osmium, ruthenium and iridium. When they are treated with aqua regia, the insoluble residue which remains, chiefly consists of an alloy and osmium, iridium, ruthenium and rhodium. To separate the osmium from the other metals, Fremy takes advantage of its easy oxidability, and of the volatility of its tetroxide.

In the first part of this process (which is a great improvement upon the methods previously followed) the above residue or alloy is heated to redness in a platinum or porcelain tube. In that part of the tube which projects from the furnace, some fragments of porcelain are placed, and the tube is connected with a series of gla.s.s flasks, in which the tetroxide of osmium is condensed as it distils over, any tetroxide that may have escaped condensation is retained by a solution of caustic potash, placed in the last flask of the series. This last flask is connected with an aspirator, by means of which a current of air is drawn through the apparatus.

Before being allowed to enter the heated tube the air is dried by being made to pa.s.s through tubes filled with pumice-stone, moistened with sulphuric acid. During the operation the osmium and ruthenium become oxidised, the tetroxide of osmium condenses in needles in the flasks, and mechanically carries forward the deoxide of ruthenium, which is deposited upon the pieces of porcelain.

There are several processes for obtaining osmium in the metallic condition. We give two of the most simple of these. 1. By treating the volatile tetroxide of osmium obtained by Fremy's method, as above described, with hydrochloric acid and metallic mercury in a closed vessel at 140 C.

The mercurous oxide which is first formed at the expense of the oxygen contained in the tetroxide of osmium is decomposed by the hydrochloric acid, and calomel is produced, together with metallic osmium.

The water and excess of acid are removed by evaporation to dryness, and on heating the residue in a small porcelain retort, the excess of mercury and calomel is drawn off, pure osmium being left behind in the form of a fine powder.

2. Deville and Debray procure it in the metallic form by pa.s.sing the tetroxide of osmium, in a current of nitrogen, over carbon which has been obtained by pa.s.sing the vapour of benzine through a porcelain tube at a high temperature. The metal procured by this process is of a fine blue colour, with a tinge of grey.

The specific gravity of osmium in the pulverulent form is about 10; but after having been heated to the fusing point of rhodium in the oxyhydrogen jet, it acquires a density of 214, and in the crystalline state it has a sp. gr. of 22477. Osmium appears to be the least fusible of all the metals.

There are five known oxides of osmium:

=1. Osmium protoxide.= (OsO). The anhydrous protoxide is of a greyish-black colour. It is insoluble in acids. Its bluish-black hydrate, which dissolves in hydrochloric acid, forms a solution of osmium dichloride of a deep indigo blue colour. The solution absorbs oxygen readily, and becomes converted into the tetrachloride (OsCl_{4}).

=2. Osmium sesquioxide.= (Os_{2}O_{3}.) This has never been isolated. Its salts, which are uncrystallisable, are of a rose-red colour.

=3. Osmium dioxide.= (OsO_{2}.) This is black.

=4. Osmium trioxide.= (OsO_{3}.) This possesses feebly acid properties. It has never been obtained in a separate form; with pota.s.sium it forms a crystalline, sparingly soluble compound, having the composition K_{2}OsO_{4}, 2H_{2}O, a dipota.s.sic osmite.

=5. Osmium tetroxide.= _Syn._ OSMIC ACID (OsO_{4}). This oxide may be obtained by operating, according to Fremy's process, on the ores of platinum, as already described. It is also formed when metallic osmium is heated with pota.s.sic nitrate, or roasted in air. It crystallises in colourless, transparent, flexible needles, which fuse easily, and dissolve readily in water. Its aqueous solution, however, does not redden litmus.

Tetroxide of osmium is converted into vapour at about 100C. The fumes are excessively irritating and deleterious, and have an odour somewhat like that of chlorine. This oxide unites with alkalies, but not with acids. It is given off as tetroxide when the alkaline solution which contains it is boiled. If applied to the skin, this oxide becomes partially reduced, and imparts a permanent black colour to the skin, due to the deposition of metallic osmium. With tincture of galls its solutions give a distinctive blue precipitate.