2. Geissler's burette. This instrument differs from Gay-Lussac's in having the narrow tube inside, instead of outside the wider one. It is found very convenient in use, and is less liable to fracture than Gay-Lussac's.
3. Mohr's burette, which can be more easily and readily managed than either of the two preceding ones, is described and figured under ALKALIMETRY.
[Illustration: Gay-Lussac's Burette and Geissler's Burette.]
In volumetric analysis the method of taking the readings of the burette is an operation of great importance, requiring considerable method and practice.
The first proceeding is to bring the eye to a level with the fluid, and to adopt a fixed and unalterable standard of what is to be considered the surface.
If you hold a burette partly filled with water between the eye and a strongly illumined wall, the surface of the fluid presents the appearance shown in fig. _a._ If you hold close behind the tube a sheet of white paper with a strong light falling on it, the surface of the fluid will present an appearance similar to that shown in fig. _b._
In both cases you have read off at the lower border of the dark zone, this being the most distinctly marked line. Its distinctness may be heightened by adopting Mohr's contrivance which consists in pasting on a sheet of very white cardboard a broad strip of black paper, and when reading off holding this close behind the burette in a position to place the border line between white and black from 2 to 3 millimetres below the lower border of the dark zone as shown in figure _c._
[Illustration: _a._ and _b._]
[Illustration: _c._]
Great care must be taken to hold the paper invariably in the same position, since if it be held lower down, the lower border of the black zone will move higher up.
To test the correctness of the graduation of a burette proceed as follows:--Fill the instrument up to the highest division with water at 608 F., then let the cubic centimetres of the liquid flow out into an accurately weighed flask, and determine the weight of these ten cubic centimetres in the usual way; then let another quantity of ten cubic centimetres flow out, and weigh again, and repeat the operation till the contents of the burette are exhausted. If the instrument is correctly graduated, every ten cubic centimetres of water at 608 F. must weigh 9990 grammes.
=BURG'LARIES.= The common precautions of locks and bolts, alarum-bells and fire-arms, are frequently found useless in preserving houses from burglars; but a light in the upper part of the house, or a small dog on the ground-floor, with the means of running into a place of safety from its enemies, has been seldom known to fail. A combination of the two would undoubtedly be doubly effective. The bark of the dog and the fear of detection by the approach of the light would deter the majority of rogues of common pluck and feeling. A dog out of doors, and consequently accessible, however large and fierce, is easily pacified or silenced by men of the class referred to.
=BURLS, REMOVAL OF, from Cloth and Wool.= Introduce the wool or the woollen goods into 100 litres of sulphuric acid at 6 B., in which 500 grams of alum and 250 grams of salt have been dissolved. Work in this bath for one or two hours, drain in the centrifugal, and hang up at 100 to 120. Wash for an hour and a half in clear water, treat for two hours with fuller's earth, soda and lime, and wash again for two hours. Sulphuric acid is adapted only for whites and indigo blues. For coloured goods solutions of chloride of tin, and chloride of manganese at 6 B., are recommended.
=BURNS[234] and Scalds.[235]= _Treatm._ When the injury is superficial and slight, a little creosote may be applied to the part. If a scald, the vesicle should be first pierced with a needle, or what is better, snipped with a pair of scissors, and the water which it contains should be then gently squeezed out. When creosote is not procurable, a liniment formed of equal parts of soft soap, basilicon ointment, oil of turpentine, and water, may be used instead. When the part feels very hot and painful, a poultice may be applied, on the surface of which a few drops of creosote, or of the liniment, should be spread with a knife. This treatment will generally succeed in allaying the pain. It may be followed by a dressing of zinc ointment, or any other like simple emollient or unctuous preparation. Creosote, contrary to what is commonly asserted, produces scarcely any smarting or pain; whilst it rapidly removes the burning sensation, and the charred surface soon assumes a dry scabby appearance, which, by dressing with simple ointment, soon comes off and leaves the part beneath in a sound and healthy state. If a poultice be applied it is best to keep it on until the next day. Plunging the part into very cold water immediately after the receipt of an injury of this kind will frequently prevent any further remedy being required. Flexible collodion painted over a burn forms a good protective envelope. In all cases cooling laxatives should be administered; and the diet should be rather low until the inflammatory symptoms subside.
[Footnote 234: BURN, s. sing.; AMBUS'TIO, L. BRLURE, Fr.; BRAND, BRANDMAHL, Ger.]
[Footnote 235: See SCALDS (under _S_).]
_Treatment for Animals._ Carbolic dressing, exclusion of air, cotton wool, linseed oil and lime water.
=BURNING-GLASS.= See LENS.
=BUTEA FRONDOSA=, _Roxb._ (Ind. Ph.) _Syn._ BENGAL KINO TREE. _Habitat._ Common all over India.--_Officinal part._ The inspissated juice obtained from the stem by incision (_Buteae Gummi_, _Kino Bengalensis_, _Bengal kino_). It occurs in the form of irregular shining fragments, seldom as large as a pea; more or less mixed with adherent pieces of greyish bark; of an intense ruby colour and astringent taste; soluble, but not freely so, in water and in alcohol. Its astringency is due to the presence of tannic and gallic acids.--_Prop. & Uses._ Similar to those of kino, for which it has been found an efficient substitute.--_Prep._ Same as those of kino.
=BUTTER.= [Eng., Ger.] _Syn._ BUTY'RUM, L.; BEURRE, Fr.; BUTER, BUTERA, Sax. The fatty matter obtained from cream by churning it.
_Manuf._ The process of making butter by the common operation of churning is extremely simple, and is well known. The chief objects to attend to are maintaining a proper temperature, and a certain degree of exposure to the air. Extreme cleanliness must also be observed; the churn and other utensils being frequently scalded out with water. When the butter is 'come,' it should be put into a fresh-scalded pan, or tub, which has been standing in cold water, cold water poured on it, and after it has acquired some hardness, it should be well beaten with a flat board until not the least taste of the butter-milk remains, and the water, which must be often changed, becomes quite colourless and tasteless. A little salt may then be worked into it; after which it may be weighed and made into 'forms,' which should then be thrown into cold water contained in an earthen pan provided with a cover. In this way nice and cool butter may be obtained in the hottest weather.
At Dumbarton the newly separated butter is put into a clean vessel, and a corn sickle is drawn several times crosswise through it, to extract any hairs that may adhere to it. This operation is performed in very cold spring water, and is followed by thoroughly washing it therein. 10 oz. of salt are now added to every stone-weight of the butter, and well mixed in.
In Devonshire the milk is generally scalded in copper pans over a charcoal or wood fire, and the cream collected as soon as it rises, or, and more frequently, when the whole has got cold. It is then churned in the usual way. On the small scale the butter is commonly obtained from this cream by patiently working it with the hand in a shallow pan or tub. Without care the cream is apt to absorb some of the fumes from the charcoal, which impart a peculiar taste to the butter. This is the reason why some of the Devonshire butter has a slight smoky flavour. It may be removed by thorough washing in cold water. Of late years, in the large dairy-farms of Devonshire, covered flues, with openings to receive the bottoms of the pans, have superseded open fires, by which the danger of contamination from the fumes is removed.
_Choice._ Fresh butter has a pleasant odour and is of an equal colour throughout its substance. If it smells sour, the butter-milk has not been well washed out; and if it is streaked or veiny, it is probably mixed with stale butter or lard. A good way to try butter is to thrust a knife into it, which should not smell rancid and unpleasant when withdrawn. Rancid and stale butter, when eaten in quantity, is capable of producing dangerous symptoms.
_Pur._ The cheaper kinds of butter are frequently adulterated with common wheat-flour, oatmeal, pea-flour, lard, and is sometimes mixed with suet and turnips, as well as with a large quantity of salt and water. The trick is concocted between the Irish factors and the London dealers. The higher priced article is seldom mixed with anything beyond an excess of salt and water, notwithstanding the assertions of alarmists to the contrary. The presence of lard may be detected by the flavour and paleness of the colour. A little of the sample adulterated with the other substances named, if melted in a glass tube or phial, will separate into strata, which are very marked when cold.
_Quantitative Analysis of Butter._--1. The following process for the analysis of butter, by Mr A. H. Allen, is extracted from the 'Chemical News' (xxxii, 77):--The Society of Public Analysts has adopted 8000 per cent. as the lowest limit of fat contained in a genuine butter.
The amount of water is best ascertained by heating 5 grams of the butter in a small weighed beaker to a temperature of about 110 or 120 C. for an hour or so. Some chemists merely heat the butter on a water bath.
According to the author's experience, perfect drying is next to impossible at that temperature.
The dried butter is next treated in the beaker with anhydrous ether, or commercial benzoline. The former liquid is expensive and inconveniently volatile, while it must be used in a perfectly anhydrous condition (to avoid solution of the salt), and except when boiling has but a limited solvent power for butter, especially when adulterated. Benzoline dissolves fat more readily than ether; it does not volatilise so rapidly at ordinary temperatures, it is always anhydrous and has the advantage of low price.
The "benzoline" employed by the author is made by redistilling the commercial article from a retort immersed in a bath of boiling water.
About one third of the original bulk usually comes over readily at 100 C., and has a gravity of 0689.
On warming the beaker containing the benzoline the dry butter readily dissolves. The liquid is poured on a small dry filter and washed with warm benzoline, the filtrate being collected in a small wide beaker. If the filter had been previously weighed, its increase of weight, after careful drying, will of course give the quantity of curd and salt in the 5 grams of butter taken. Except in cases in which extreme accuracy is desired, it is preferable to scrape the residue off the filter and weigh it separately.
The error (owing to imperfect removal) only amounts to one or two tenths per cent. of the butter taken. As the salt is accurately estimated afterwards, the loss falls on the curd. The salt may be determined by careful ignition of the filter and residue, the incombustible matter consisting almost wholly of common salt, while the curd is ascertained by loss of weight. This method is not to be recommended; for without great care some of the salt will be volatilised and lost, the error causing the amount of curd to appear excessive.
Ignition also renders any further examination of the curd an impossibility. A far preferable plan is to return the weighed curd and salt to the filter, and to wash them with cold water. The filtrate is made up to 100 c. c., and the salt is estimated in a half of it by titrating with decinormal nitrate of silver. The remaining portion of the solution can be employed for the estimation of sugar, if desired. This is effected by inverse titration with Fehling's copper solution, in the same way as grape sugar. The estimation of sugar may sometimes be of interest, as a means of ascertaining whether the aqueous portion of the butter consisted of mere water or of serum of milk. In other words, the estimation of the sugar may furnish a means of ascertaining whether an excess of water in the butter is due to insufficient removal of the butter-milk, or to subsequent incorporation of water. Every 0001 gram of milk sugar represents about 0022 of average milk serum.
The residue insoluble in cold water usually consists almost wholly of casein. If, however, the butter has been adulterated with mashed potatoes, flour, or other starchy matters--said to be occasionally employed--they will be found here. The presence of starch in the residue will, of course, be readily indicated by treating it with hot water, and testing the cooled liquid with solution of iodine. By pressing out a small portion of the butter between two slips of glass, so as to obtain a thin film, and observing it under the microscope (or by observing the caseous residue after treatment with cold water), the nature of the starch may be ascertained.
The solution of the fatty matter in benzoline is evaporated at 100 C.
till it no longer decreases in weight. The average proportion of fatty matter in butter is about 85 per cent. If less than 80 per cent. the butter must be considered adulterated. It is evident that a careful estimation of the per-centage of fatty matter would often render separate estimations of the water, curd, and salt unnecessary; for unless the sum of the three latter constituents exceeded 20 per cent. the butter could not be considered as adulterated, unless by an admixture of other fats.
An easy and rapid method of estimating the fat in the undried butter is therefore a great desideratum; but unfortunately no satisfactory method is at present known. The indirect estimation of the fat, by subtracting the sum of the per-centages of water, curd, and salt from 10000, ought to agree with the direct estimation of fat within 05 per cent., and the variation is often much less.
2. Dr Dupre adopts the following method: About 5 grams of the dry filtered butter fat are weighed in a small strong flask; 25 c. c. of a normal alcoholic soda solution are added; the flask is closed by means of a well-fitting cauotchouc stopper, firmly secured by a piece of canvas and string, and heated in a water-bath for about an hour. When cool the flask is opened, the contents--which are semi-solid--carefully liquefied by heat, and washed into a flask with hot water. This flask is now heated for some time on a water-bath to expel the alcohol, some more hot water is added, and 25 c. c. of diluted sulphuric acid somewhat stronger than the alkali used, are run in. The contents are allowed to cool, and the acid aqueous solution below the cake of fatty acids is passed through a filter.
The fatty acids in the flask are washed by hot water in the manner recommended by Dr Muter, _i.e._, each time allowed to cool; all the washings are passed through a filter.
The author uses no cambric, but passes everything through paper. With care scarcely any of the fatty acid will find its way into the filter. After the washing with water is completed and the flask drained, he washes any fatty acid that may be on the filter into the flask by means of a mixture of alcohol and ether on a water bath, and finally dries the fatty acids in the flask at a temperature of 105 C. The drying can be done readily if the melted fat is now and then shaken briskly, so as to subdivide the water as much as possible. In this way the acids when once in the flask are not taken out until their weight has been taken, thus reducing the risk of loss to a minimum. Meanwhile the acidity of the aqueous filtrate and washings is estimated by decinormal soda solution. Subtracting from the amount required to the proportion necessary to neutralise the excess of acid added in decomposing the soap, the rest represents the soluble fatty acids contained in the butter taken, and on the assumption of its being butyric acid, we can, of course, calculate the amount of this acid present. When once the equivalent of the soluble acids present in butter is fairly determined, this, of course, will have to be substituted for that of butyric acid. The results thus obtained are very accurate, and the process is very simple in execution.
The author has satisfied himself by repeated experiments that the alkalinity of the alcoholic soda solution by itself is not altered by the process. The author places no reliance on the specific gravity test, as he finds that mutton dripping, and other fats likely to be used as adulterants of butter, may acquire a specific gravity above 911 by being strongly and repeatedly heated. He thinks, however, that any sample of butter below 911 may safely be pronounced adulterated.
In a subsequent note Dr Dupre states that he has effected the saponification, decomposition of the soap, and the washing and drying of the fatty acids at ordinary temperature, thus still further reducing the risk of breaking up the higher into lower acids. The saponification is readily effected by using a sufficiency of alcoholic soda. Between four and five grams of the dry butter fat were shaken up for several minutes with 100 c. c. of normal alcoholic soda. The butter soon dissolves, but after a time the solution gelatinises to a clear transparent mass. (The temperature of the laboratory at the time of these experiments ranged between 22 and 50.) This jelly is now allowed to stand over night, during which time the smell of butyric ether, very strong at first, entirely disappears. In one of the experiments the alcohol was allowed to evaporate spontaneously before the acid was added; in the other (made with a different sample of butter) the soap was dissolved in about half a litre of water, and at once decomposed by the addition of hydrochloric acid.
The fatty acids which separated in white curdy masses were thoroughly washed on a filter with cold water, about four litres, dried in vacuo over oil of vitriol, and weighed. The results of experiment show that butter fat yields the same proportion of insoluble fatty acids when saponified with or without the aid of heat.
3. Mr Gatehouse. _Rapid Method of Detecting the Adulteration of Butter with other Fats._ The following comparative method is based upon the insolubility of potassium stearate in alkaline solutions when the stearate has been produced at high temperatures:
Before applying the test it is essential to remove all curd, butter-milk, and salt, by washing with hot water or dissolving in ether. Twenty grains of the butter are placed in a large test-tube one third full with water boiled thoroughly and allowed to stand till the fat separates. The fat is either dissolved in ether, and after evaporation saponified, or the lower layer of the liquid is drawn off by a pipette as follows:--A thin glass tube is drawn out to a fairly fine point and bent at the top to an obtuse angle. Whilst the butter is still liquid this nozzle is inserted into the bottom of the test-tube, placing the finger over the upper end to prevent any liquid from getting in till it reaches the bottom. When fairly cold the liquid may be withdrawn by a pipette attached to the tube. This process can be repeated till the washings are free from chlorides.
The saponification is effected by heating the purified butter with 1/3-1/2 of its own weight of pure solid potassium hydrate (purified by alcohol) to a temperature above 420 F.; applying the heat gently at first, and when the frothing ceases, heating it more strongly, till no further apparent action occurs. The ultimate temperature during saponification must be kept above 400 for some minutes, otherwise the sterate formed will be soluble instead of insoluble in the alkaline solution.
If the butter is pure, the colour of the residue will be at the utmost light yellow, but should the butter be adulterated to any extent, it may be almost black. Too much reliance must not, however, be placed on the colour.
After allowing the tube and its contents to cool, the mass is boiled with successive portions of distilled water till 6 oz. (or 200 c. c.) altogether have been used. If the butter is pure, a portion of this solution poured into a test-tube will present only a faint opalescence; if, on the other hand, the butter is impure, a decided opacity will be perceived, the degree depending upon the amount of adulteration.
The amount of adulteration in any sample is determined by first obtaining pure butter and adding to separate portions of it known per-centages of lard, &c. Each of these can be saponified as stated above; they are then corked up in tubes of equal diameter and labelled with the per-centage of lard they contain. On comparing them it will be seen that 2 per cent. of lard can be clearly indicated.
When a butter is analysed all that is wanted is to saponify, make up to the correct strength, and after cooling pour into a test-tube and compare with the specimen tubes.
4. Dr Redwood. _The Determination of the Melting Points of Butter and other Fats._ The apparatus in the form best suited for general use consists of a basin, two small beakers, and a thermometer. The author uses an enamelled iron basin about six inches in diameter, and three and a half inches deep. In this is placed a beaker four and a half inches deep and three inches in diameter, and within this beaker is placed another much smaller one, supported by its projecting rim on a disk of tinplate or copper, the outer edge of which rests on the mouth of the larger beaker.
Some mercury is put in the smaller beaker to the depth of about an inch, and cold water into the larger beaker, so that its surface shall be half an inch or an inch higher than that of the mercury.