Chapter LXXVI: Part 2 (37)

=Tea, Lie.= Of this compound, Dr Hassall says:——“It is so called because it is a spurious article and not tea at all. It consists of dust of tea leaves, sometimes of foreign leaves and sand made up by means of starch or gum into little masses, which are afterwards painted and coloured, so as to resemble either black or green gunpowder. The skill exhibited in the fabrication of this spurious article is very great, and we have met with at least a dozen varieties of it, differing from each other in the size and colouring of the little masses.”

The once notorious ‘PARAQUAY PLANT,’ sold in packets, was simply new meadow-hay that had been wetted with a strong infusion of catechu, then dried, chopped small, and strongly compressed. See THEINE and CAFFEINE.

=Tea.= “The tea is not a meal; when it is properly used, it should not be a meal; but it has a special purpose to fulfil, which I will now explain. Tea——and under the generic term tea I include coffee——tea is usually taken three hours after dinner. This is the moment which corresponds with the completion of digestion, when, the food having been conveyed away from the stomach, nothing remains behind but the excess of the acid juices employed in digestion, these acid juices create an uneasy sensation at the stomach, and a call is made for something to relieve the uneasiness; tea fulfils that object.” “On the same principle, after the business of the dining-room, the antacid and refreshing beverage, either in the shape of tea or coffee, is prepared in the drawing-room. In taking either, the nearer they approach to the simple infusion the better; little milk or cream, and less sugar, should be the principle. But, seeing the purpose of tea, how unreasonable to make it the excuse for a meal, to conjoin with it toast, muffins, bread and butter, and _id genus omne_.” “Three meals a day may be taken as the standard of habit and custom; tea and coffee having a specific place and purpose as a beverage, but none as a meal.” (Eras. Wilson.) See MEALS, &c.

Although tea is undoubtedly prejudicial to children and to adults of nervous and irritable temperament, there can be no question that, if its use be not abused, it possesses valuable physiological properties. On the nervous system it acts as a pleasant stimulant and restorative, its moderate use not being followed by depression. Dr Parkes says these effects are in some measure due to the warmth of the infusion. According to the same authority its use is followed by very little quickening of the pulse, whilst there is an increase in the amount of perspiration, and a slightly diminished action on the bowels. Cases, however, are not uncommon in which this latter effect is reversed.

Dr Edward Smith says that tea increases the excretion of pulmonary carbonic acid. The contention that the elimination of urea is lessened, does seem to have been not satisfactorily established. If so, the diminution is very trifling. Sir Ranald Martin says tea is most useful against excessive fatigue, especially in hot climates. The traveller in the Australian bush speaks highly of its renovating effects at the end of a long day passed in the saddle.

A cup of strong green tea without milk or sugar is a popular and frequently by no means inefficient remedy for a severe nervous headache. According to Liebig, tea and coffee resemble soup in their effect on the system. Lehmann’s experiments seem to show that they lessen the waste of tissue in the human body. Tea taken too continuously, or in excess, produces indigestion, flatulence, and constipation, besides rendering its votaries anæmic and depressed in spirits.

It is a fallacy to suppose that soft water makes the best tea. It certainly yields a darker infusion than that made from moderately hard water, but this is owing to the soft water taking up a large quantity of bitter, physiologically inert, extractive matter from the tea, the delicate flavour of which becomes thereby greatly impaired. This is why connoisseurs object to an infusion of too dark a colour. Moderately hard _boiling_ water, on the contrary, fails to dissolve this objectionable ingredient, and hence produces a beverage in which the characteristic taste of the pleasant aromatic principle of the tea is not masked by the bitter substance. London water, which, when boiled, has a hardness of about 5 degrees (equal to 5 grains of lime salts to the gallon), makes excellent tea——better, in fact, than a water of half the hardness, the latter yielding a slightly bitter infusion. In the use of moderately hard water, it is essential that it should be allowed to remain on the tea sufficiently long. The Chinese never employ either very soft or immoderately hard water, but _a water of medium hardness_.

“Experimentally it is found that infusions of tea and coffee are strong enough when the former contains 0·6 per cent. of extractive matter, and the latter 3 per cent., so that a moderate-sized cup (5 oz.) should contain about 13 grains of the extract of tea, or 66 grains of coffee. These proportions will be obtained when 263 grains of tea (about 2-1/2 teaspoonfuls) or 2 oz. of freshly-roasted coffee are infused in a pint of boiling water; and the amounts of the several constituents dissolved are about as follows:——

“Constituents. Tea. Coffee.
grs. grs.
Nitrogenous matters 17·2 44·0
Fatty matter —— 3·0
Gum, sugar, and extractive 31·7 103·2
Mineral matters 9·1 22·8
———— ——————
Total extracted 58·8 173·0

“So that tea yields, to a pint of fresh water, about 22 per cent. of its weight, and coffee about 20 per cent. Lehmann found that only 15-1/2 per cent. of tea was dissolved by water, whereas Sir Humphry Davy estimated it at 33-1/2 per cent. No doubt the quality of the water, as well as that of the tea, affects the results, for cold distilled water will extract from 40 to 44 per cent. of black tea, and nearly 50 per cent. of green; but, for all this, about 22 per cent. is a good average with boiling water.”[226]

[Footnote 226: Letheby, ‘Lectures on Food.’ Longmans.]

Dr Edward Smith has shown in the following table that, when the usual custom of measuring tea into the teapot by the spoonful is followed, very varying weights of tea are employed. Thus he found that the weight of a spoonful of tea was for——

_Black Teas._

Oolong 39 grains.
Congou (inferior) 52 ”
Flowery Pekoe 62 ”
Souchong 70 ”
Congou (fine) 87 ”

_Green Teas._

Hyson 66 grains.
Twankay 70 ”
Fine Imperial 90 ”
Scented Caper 103 ”
Fine Gunpowder 123 ”

The attempt to make good tea will prove a failure unless the water employed is _boiling_. Previously to making the infusion, the teapot should always be warmed up by means of boiling water. The kettle should be filled from the _tap_, and not the boiler. It should also be borne in mind that neither good tea nor coffee can be obtained if they are made with water that has been in the kettle for many hours. The tea is ready to be drank after the boiling water has stood on it for five minutes.

=Tea, Beef.= _Syn._ INFUSUM CARNIS BUBULÆ, JUSCULUM CUM CARNE BOVIS, L. This is merely a very concentrated soup formed of lean beef. According to the common plan, lean beef, 1 lb., is gently simmered in water, 1 quart, for about 1/2 an hour, when spices, salt, &c., are added, and in a few minutes the whole is strained for use. The following are other formulæ:

1. (Dr A. T. Thomson.) Take good rump steak, 1/2 lb.; cut it into thin slices, spread these over a hollow dish, sprinkle a little salt on them, add a pint of boiling water, and place the dish (covered) near the fire for 1/2 an hour; then remove the whole to a saucepan, and boil it gently for 15 minutes; lastly, strain through a hair sieve.

2. (Prof. Liebig.) Beef, free from fat, 1 lb., is to be minced very small, mixed with an equal weight of cold water, and, after digestion and agitation in the cold for about 1/2 an hour, heated slowly to boiling; when it has boiled for a minute or two, strain it through a cloth. It may be coloured with roasted onion or burnt sugar, and spiced and salted to taste.

_Obs._ Similar preparations are ordered in some foreign Pharmacopœias from calves’ lights, crayfish, frogs, mutton, pullets, snails, tortoise, veal, &c. In the Ph. L. 1746 a form was given for viper broth (JUSCULUM VIPERINUM). See ESSENCE OF BEEF, EXTRACT OF MEAT, &c.

=TEETH (The).= _Syn._ DENTES, L. An object very subservient to health, and which merits due attention, is the preservation of the teeth; the care of which, considering their importance in preparing the food for digestion, is, in general, far from being sufficiently appreciated. Comparatively very few persons wash their mouth and clean their teeth even once a day; a feat which ought always to be practised at the conclusion of a meal, when either animal food or vegetables are eaten; for the first is apt to leave behind it a rancid acrimony, and the other an acidity, both of them hurtful to the teeth. Those who abhor a fetid breath, rotten teeth, and the toothache, would do well to invariably clean their teeth before retiring to rest. With smokers, this practice is almost obligatory. Washing the mouth frequently with cold water is not only serviceable in keeping the teeth clean, but in strengthening the gums, the firm adhesion of which to the teeth is of the greatest importance in preserving them sound and secure. Some persons think it serviceable to add a few drops of spirit or essence of camphor to the water thus employed, a plan we certainly approve of. See BREATH, DENTIFRICES, PASTES, POWDERS, TOOTH CEMENTS, WASHES, &c.

=Teeth, Stoppings for.= See DENTISTRY.

=TEETH′ING.= _Syn._ DENTITION. Children are sometimes born with one or more teeth; but, in general, the teeth, at birth, consist of mere pulpy rudiments buried in the gum. Their development is gradual. About the third or fourth month they begin to assume shape and hardness. At this period children become fretful, the saliva flows copiously, the gums grow turgid, and there is a fondness of biting hard cold objects. In nearly all cases there is more or less fever, frequently a cough or diarrhœa, and a rash commonly appears, which is called by nurses the ‘red gum.’ These symptoms generally abate after a fortnight or three weeks, and the child remains undisturbed until the seventh or eighth month. About this period the gums again become red, tender, and swollen, and often extremely sensitive, and painful. The upper part of the gum gradually becomes attenuated and pale, and, just before the tooth appears, even covered with a blister. These changes are usually attended by an increased flow of saliva, or ‘drivelling,’ and a lax state of the bowels, both of which are regarded as favorable symptoms. Sometimes, however, the diarrhœa is excessive, when it may be cautiously restrained by a dose or two of rhubarb-and-magnesia, with a little dill or peppermint water; or, better, by the daily use of a little arrow-root, to which a few drops of pure port wine may be added. Sometimes the local irritation is considerable, or there are spasms or convulsions, in which case the practice is to lance the gums. When there is drowsiness, stupor, or oppressed respiration, one or two leeches may be applied to the temples, and a small blister to the back of the neck, or behind the ear. Sluggishness of the bowels may be removed by a little castor oil; or, when there is actual constipation, by a little calomel or mercurial powder and rhubarb. Excessive irritability, without other marked symptoms, is best combated by a drop or two of tincture of hops in sweetened water. Throughout the whole period of dentition the use of warm dry clothing, freedom from tight bandages, with thorough ventilation, good nursing, exercise, fresh air without undue exposure, abundance of crawling on the carpet, and frequent warm baths, will be found most advantageous. Indeed, the last, without other treatment, are often sufficient to subdue the most distressing convulsions and the most obstinate diarrhœa, and in no case can they do harm. See NURSING, STROPHULUS, &c.

=TELEPHONE.= Within the memory of the present generation Sir Charles Wheatstone made some experiments on the transmission of sound, which were subsequently repeated and enlarged upon by Professor Henry in America. Connecting together by means of a bar of wood the sounding boards of two pianos placed in houses on opposite sides of the street, Henry found that when the piano on one side of the street was played upon the musical sounds it gave out were reproduced by that on the other side. The next research in this direction was that of Page, in 1837, who, setting up vibrations in bars of iron, by rapidly magnetising and demagnetising them elicited from them musical notes corresponding with the velocity of the vibration. Similar effects, but more marked in character, were produced by De la Rive, in 1843, by means of a succession of electric currents transmitted through a copper wire stretched through a cylinder made of insulated copper wire.

In 1861 Reiss, of Freidrichsdorf, perfected an instrument which, by means of the vibrations of a diaphragm alternately completing and breaking the continuity of a galvanic circuit, reproduced musical sounds in an iron bar at a distance.

Varley, in 1870, obtained similar results to Reiss by the rapid charging and discharging of a condenser.

In the first of these experiments——viz. Henry’s——the sound was mechanically conducted along the bar of wood from the strings of one piano to those of the other, which, being thrown into similar vibratory movements gave rise to similar sounds.

In the other experiments, on the contrary, the sounds were not due to the chemical conduction at all, but to currents of electricity. It has been explained that Reiss’ instrument was capable of reproducing musical sounds at a distance from their origin. Reiss’ may, therefore, be regarded as the original telephone. But, although able to reproduce a musical note or sound originating at a distance, this instrument failed altogether in the case of a word or a sentence, for the simple reason that the current of electricity which passes through the wires is an intermittent one. Musical sounds differ in tone, in intensity, and quality. The tone depends upon the number of vibrations produced in the air per second; when these are less than sixteen no sound is produced. The intensity is due to the extent or amplitude of the vibrations; and the quality or _timbre_, to the form of the undulations made by the vibrating particles of the atmosphere. Now, of all these qualities or varieties of sound, the first only, or the tone, can be reproduced by a current of intermittent electricity, so that Reiss’ is a _tone_ telephone, and as such is only capable of redelivering a number of musical notes. To Professor A. Graham Bell alone belongs the merit of having invented an _articulating_ or _speaking_ telephone, or an apparatus by means of which not only tone, but intensity and _timbre_ of sound——in short, speech in its entirety can be electrically conveyed from one point to another, no matter how distant. The practical result of this is that a conversation can be carried on, the distance by which the speakers may be separated being of no import. To the particular species of electricity by which this is accomplished Professor Bell has given the name ‘undulatory,’ in contradistinction to ‘intermittent’ or ‘pulsatory.’ The annexed plate, which is half the actual size of Bell’s articulating telephone, represents that instrument in section.

_m m_ is a permanent bar-magnet, to the upper end of which is attached a soft iron core, which becomes magnetised by the permanent magnet. Surrounding the iron core is a coil of very fine insulated copper wire (_b_), the two ends of which are carried to the terminals (_t t_), by means of which one is connected with the line wire, and the other with the earth, _d_ is a disc of thin iron plate, either tinned or japanned, about the size of a crown piece, and _c_ is the cavity or mouth-piece. Upon applying the lips to this and speaking into it, the iron disc (_d_) vibrates towards the soft iron core, the result being that a current of induced electricity is set up in the coil (_b_), Which, being in connection by means of the telegraph wire with a precisely similar arrangement at the other end of the line, reproduces there the spoken words by means of a corresponding disc. The magnet with its attachments are enclosed in a wooden case (_a a_, _a a_, _a a_); _n n_ are screws which secure the iron disk (_b_); _s_ is a screw for adjusting the distance between the polo of the magnet and the disk (_b_).

The extreme simplicity of Professor Bell’s telephone was the outcome of several antecedent experiments, worked out by forms of apparatus gradually diminishing in complexity.

The German physicist Helmholtz had previously shown that by the agency of a current of intermittent electricity passed through a tuning-fork, he could produce simultaneous vibrations in a number of other forks connected with the first by a wire, and that by varying the loudness of these vibrations by means of resonators, so as to combine the musical notes in different proportions, the resulting sound was an imitation of certain vowel sounds, or a copy of the _timbre_ of sound.

Professor Bell’s first telephone was an extension of Helmholtz’s device for producing vowel or composite sounds. A number of steel wires of different pitch were made into a harp, and connected by a powerful permanent magnet, the same arrangement being repeated at the other end of the circuit. In the magnetic field of the permanent magnet was an electro-magnet. When a permanent magnet is vibrated in the neighbourhood of an electro-magnet, this latter will have a current of electricity generated in it, the intensity of which will vary with the velocity of the vibrations in the permanent magnet, whilst it will be either positive or negative according to the direction of these same vibrations. So that a vowel sound, if produced by causing a number of the rods of the harp to vibrate at the same time, can be transmitted by a current of electricity, and will be reproduced by the harp at the other end of the connecting wire. If a piano were sung into whilst the pedal was down, not only would the pitch of the voice be echoed back, but an approach to the quality of the vowel would also be obtained. And theory teaches that if the piano had a very much larger number of strings to the octave, we should get not only an approximation to, but an exact vocal reproduction of the vowel. If, therefore, in the harp there were a large number of steel rods to the octave, and you were to speak in the neighbourhood of such a harp, the rods would be thrown into vibration with different degrees of amplitude, producing currents of electricity, and would throw into vibration the rods at the other end with the same relative amplitude, and the _timbre_ of the voice would be reproduced.

The effect when you vibrate more than one of these rods simultaneously is to change the shape of the electrical undulation, and a similar effect is produced when a battery is included in the circuit. In this case the battery current is thrown into waves by the action of the permanent magnets. Hence you will see that the resultant effect on the current of a number of musical-tones, is to produce a vibration which corresponds in every degree to the moving velocity of the air. Suppose, for instance, you vibrate two rods in the harp, you have two musical notes produced, but of course if you pay attention to a particle of air, it is impossible that any particle of air can vibrate in two directions at the same time; it follows the resultant form of vibration. One curve would show the vibration of a particle of air for one musical tone, the next one for another, and the third the resulting motion of a particle of air when both musical tones are sounded simultaneously. You have by the harp apparatus the resultant effect produced by a current of electricity, but the same resultant effect could be produced in the air. There is an instrument called the phonantograph. It consists of a cone which, when spoken into, condenses the air from the voice. At the small end of the cone there is a stretched membrane which vibrates when a sound is produced, and in the course of its vibration it controls the movement of a long style of wood, about one foot in length. If a piece of glass with a smoked surface is rapidly drawn before the style during its movement, a series of curves will be drawn upon the glass. I myself uttered the vowels _e_, _ay_, _eh_, _ah_, _aah_. These vowels were sung at the same pitch and the same force, but each is characterised on the glass by a shape of vibration of its own. In fact, when you come to examine the motion of a particle of air, there can be no doubt that every sound is characterised by a particular motion. It struck me that if, instead of using that complicated harp, and vibrating a number of rods tuned to different pitches, and thus creating on the line of wire a resultant effect, we were at once to vibrate a piece of iron, to give to that piece of iron not the vibration of a musical tone, but to give it the resultant vibration of a vowel sound, we could have an undulatory current produced directly, not indirectly, which would correspond to the motion of the air in the production of a sound.

The difficulty, however, was how to vibrate a piece of iron in the way required.

The following apparatus gave me the clue to the solution of the problem in the attempt to improve the phonantograph. I attempted to construct one modelled as nearly as possible on the mechanism of the human ear, but on going to a friend in Boston, Dr Clarence J. Blake, an aurist, he suggested the novel idea of using the human ear itself as a phonantograph, and this apparatus we constructed together. It is a human ear. The interior mechanism is exposed, and to a part of it is attached a long style of hay. Upon moistening the membrane and the little bones with a mixture of glycerin and water, the mobility of the parts was restored, and on speaking into the external artificial ear a vibration was observed, and after many experiments we were enabled to obtain tracings of the vibration on a sheet of smoked glass drawn rapidly along. This apparatus gave me the clue to the present form of the telephone. What I wanted was an apparatus that should be able to move a piece of iron in the way that a particle of air is moved by the voice.[227]

[Footnote 227: From Professor Bell’s lecture at the Society of Arts, Nov. 28th, 1877, published in the Journal of the Society, vol. 26, p. 17.]

We need not follow Professor Bell through the various stages by which he arrived at his most successful solution of this problem further than to state that the simplicity of construction exhibited in the present form of instrument did not characterise the earlier articulatory telephones. Amongst the causes contributing to this simplicity may be mentioned the abandonment of an animal membrane attached to the iron plate, the diminution of the coil of insulated wire, and the substitution for the galvanic battery which formerly formed part of the circuit, of the permanent magnet.

Professor Bell records the curious fact that hardly any difference is observable in the results by varying the size, thickness, and force of the permanent magnet, and that beyond a remarkable effect in the quality of the voice, distinct articulations might be obtained from iron plates of from 1 inch to 2 feet in diameter and from 1/64th to 1/4th inch in thickness. With plates of uniform thickness, but of varying diameter, he obtained the following results. With a plate of small diameter the articulation was perfectly distinct, but the sound emitted was as if a person were speaking through the nose. By gradually enlarging the diameter of the plate this nasal effect as gradually disappeared, until when a certain diameter was attained a very good quality of voice manifested itself.

By continuing to enlarge the diameter, a coarse, hollow, drum-like effect was produced, until when the diameter became very large, the sound resembled that one hears when the head is inside a barrel, and was accompanied with a reverberating sound. By reversing the above conditions——that is, by keeping the diameter constant, and varying the thickness——it was found that with a very thin plate the drum-like sound was produced; by gradually increasing the thickness this effect passed off; then followed distinct articulation, until at a certain increase of thickness the peculiar nasal quality again developed itself.

In practice it has been found desirable, in establishing speaking communication between two distant places, to employ two telephones instead of a single one; one being applied to the mouth and the other to the ear during a conversation.

With one telephone it was no unusual occurrence for confusion to arise in consequence of the two speakers talking or listening at the same time.

So faithful is the transmission by the telephone of every variety of sound, that Mr Preece states, when in telephonic communication with Prof. Bell, through a quarter of a mile he has heard him “laugh, sneeze, cough, and, in fact, make any sound the human voice can produce.” It must be borne in mind, however, that the transmitted speech can only be distinctly heard in the immediate vicinity of the receiving apparatus; the keenest hearing fails to detect it at the distance of little more than a foot away. Hence, when a message is expected, the recipient has to place his ear to the mouthpiece of the instrument, and use it as an ear-trumpet.

A circumstance tending to impair the satisfactory working of Bell’s telephone is, that the line wire to which the ends of the coil are attached becomes inductively affected by the currents of electricity passing through the parallel and contiguous telegraph wires, the effect, on a line where there is an active transmission of telegraphic messages, being that the telephone “emits sounds that are very like the pattering of hail against a window, and which are so loud as to overpower the effects of the human voice.”[228]

[Footnote 228: Preece.]

This inconvenience can, however, it is stated, be remedied.

If all the arrangements of the instrument were perfect, there should be no limits to the distance through which speech could be conveyed by the telephone. Professor Bell says that in laboratory experiments “no difficulty has been found in using an apparatus of this construction through a circuit of 6000 miles;” and that he had found it act efficiently between New York and Boston, a distance of 258 miles, subject to the condition that the neighbouring telegraph wires were not in action.

Mr Preece has carried on conversations between Dublin and Holyhead, a distance of 100 miles.

Two useful applications of the telephone are recorded by Professor Bell, the one its employment in connection with the diving bell; the other as a means of communication between those above and below ground in mines. It has been largely adopted in extensive factories and in commercial houses both in America and in this country, supplementing, because of its much greater simplicity and easy application, the electric telegraphs previously in use in such establishments.

We extract the following from the ‘Journal of the Society of Arts,’[229]

[Footnote 229: Vol. 26, p. 887.]

“THE TELEPHONE AND THE TORPEDO.

“A novel application of the Bell telephone is one which has been made in connection with torpedoes by Captain C. A. M’Evoy, of 18, Adam Street, Adelphi. The torpedoes to which the telephone has been applied are those of the buoyant contact class——that is, floating torpedoes, which are used for the protection of rivers and harbours. These torpedoes are held in position beneath the surface of the water by mooring lines and anchors, and it is necessary to ascertain from time to time that these deadly agents are in active working order. They are, of course, connected to the shore by electric wires by which they may be exploded. They are also arranged so that they may be exploded electrically by contact with passing vessels. For this latter purpose they are fitted with what is known as a circuit closer, which is placed in the middle of the charge within the torpedo. The testing is ordinarily performed by sending a current of electricity through the torpedo and fuse; but, in order that the fuse may not be fired, and the torpedo consequently exploded during the process of testing, an extremely weak current has to be used in connection with a sensitive galvanometer. The consequence is that the indications received are so very delicate that they are not always to be relied on. Now, what Captain M’Evoy does is to supplement the electrical test by the test of sounds, and to this end he encloses an ordinary Bell telephone in each torpedo. The telephone is so placed that the vibrating diaphragm is in a horizontal plane, and upon it are laid a few shot or particles of metal, and these are boxed in. Every motion of the torpedo causes the shot to shift their position upon the face of the diaphragm and to cause a slight noise, which is distinctly heard in the receiving telephone on shore. Thus each torpedo two or three miles away, in the restless waters of a channel, is continually telling the operator on shore of its own condition in language sometimes excited, according to the state of calmness or agitation of the water at the time. Should the torpedoes be sunk, they would lie motionless on the bottom, and the silence of the telephone would indicate the fact of their inoperativeness. The telephones are connected to the ordinary electric wires of the torpedoes, but this does not prevent them from being tested in the usual way from the battery on shore.”

=TELLU′RIUM.= A rare greyish-white elementary substance, found only in small quantities, associated with gold, silver, lead, and bismuth, in the gold mines of Transylvania. It has often been described as a metal, but is now commonly classed with the non-metals.

1. Tellurium may be obtained from the bismuth ore (the telluride of bismuth) by strongly heating the ore with a mixture of carbonate of potash and charcoal. A potassium telluride is formed which dissolves in water, forming a solution of a purplish-red colour, from which the tellurium deposits on exposure of the liquid to the atmosphere.

2. Schrötter gives the following method for the obtainment of metallic tellurium:——The raw material is treated with dilute hydrochloric acid as long as carbon dioxide is evolved, then with strong acid until all sulphuretted hydrogen is driven off.

The liquid is decanted from the residue, which is washed with hydrochloric acid and hot water, then boiled with aqua regia until the insoluble matter is white. From the aqua regia solution any gold that may be present is precipitated by means of ferrous sulphate, and afterwards zinc is added to precipitate the tellurium. The precipitate on the zinc is washed, dried, and heated to redness, treated with sulphuric acid to remove any silver, and the remaining tellurium is then collected.

Tellurium bears a great resemblance to bismuth in appearance, having a pinkish metallic lustre; it further resembles bismuth in being crystalline and brittle.

Below a red heat it enters into a state of fusion; at a high temperature it becomes converted into a yellow vapour. It burns in air, when strongly heated, with a blue flame having a green rim, and giving off white fumes that have a peculiar odour. When taken internally, even in very minute quantities, tellurium imparts to the breath an offensively powerful odour of garlic. Tellurium dissolves in cold concentrated sulphuric acid, to which it imparts a rich purple-red colour. If the acid solution be diluted with water the tellurium precipitates unchanged. There are two oxides of tellurium: the dioxide (TeO_{2}) and the trioxide (TeO_{3}), the first of which corresponds to sulphurous, and the second to sulphuric anhydride.

_Tellurous acid_ (H_{2}TeO_{3}) is obtained by pouring a solution of tellurium on nitric acid of 1·25 into water, when the tellurous acid is precipitated as a bulky hydrate. This hydrate is slightly soluble in water and reddens litmus. It forms salts called tellurites.

_Telluric acid_ (H_{2}TeO_{4}). When tellurium or tellurous acid is gently heated with nitre a potassic tellurate is formed, this being decomposed by a salt of barium, whilst the resulting barium tellurate is in its turn decomposed, and the telluric acid separated by sulphuric acid. The telluric acid occurs in hexagonal prismatic crystals, which, when heated usually to redness, becoming converted into telluric anhydride, which then assumes an orange-yellow colour. This telluric anhydride (TeO_{3}) is entirely insoluble in water, nitric and hydrochloric acids, and alkaline solutions. Although it has but a feeble attraction for bases, telluric acid forms salts which are called tellurates. There are two chlorides of tellurium: the dichloride (TeCl_{2}) and the tetrachloride (TeCl_{4}). They may both be obtained by the direct action of chlorine on tellurium.

_Telluretted hydrogen, or dihydric telluride_. (H_{2}Te). This compound presents a striking analogy to seleniuretted and sulphuretted hydrogen. Like both of these it is gaseous, but resembles the latter in smell more than the former. It burns with a blue flame, reddens litmus, and when fused into water forms a colourless solution, which becomes brown by exposure to the air, owing to the oxidation of hydrogen and the deposition of tellurmin. The salts of most of the metals are decomposed when a current of telluretted hydrogen is passed through these solutions, from which the metals are then thrown down as tellurides. These tellurides present a close resemblance to the corresponding sulphides. The tellurides of the alkali metals, like the sulphides, are soluble in water.

_Tests._ The most distinctive character of tellurium compounds is the reddish-purple solution of potassium telluride they furnish when fused with potassic carbonate and charcoal and treated with water.

=TEM′PERATURE.= In English pharmacy it is customary to measure the degree of heat by Fahrenheit’s thermometer. When a boiling heat is directed, 212° is meant. A gentle heat is that which is denoted by any degree between 90° and 100° Fahr.

Whenever specific gravity is mentioned, the substance spoken of is supposed to be of the temperature of 62° Fahr. (Ph. L.)

In the B. P., Ph. E., & D., and in chemical works in this country generally, the specific gravities of bodies are taken at, or referred to, the temperature of 60° Fahr. See THERMOMETERS.

The following data may be of use to the pharmacist:

_Degree of Fahr._
2786 Cast iron melts (Daniell).
2016 Gold melts (Daniell).
1996 Copper melts (Daniell).
1873 Silver melts (Daniell).
1750 Brass (containing 25% of zinc) melts (Daniell).
1000 Iron, bright cherry red (Poillet).
980 Red heat, visible in daylight (Daniell).
941 Zinc begins to burn (Daniell).
773 Zinc melts (Daniell).
644 Mercury boils (Daniell), 662 (Graham).
640 Sulphuric acid boils (Marignac), 620 (Graham).
630 Whale oil boils (Graham).
617 Pure lead melts (Rudberg).
600 Linseed oil boils.
518 Bismuth melts (Gmelin).
442 Tin melts (Crichton).
380 Arsenious acid volatilises.
356 Metallic arsenic sublimes.
315 Oil of turpentine boils (Kaure).
302 Etherification ends.
257 Saturated sol. of sal ammoniac boils (Taylor).
256 Saturated sol. of acetate of soda boils.
239 Sulphur melts (Miller), 226 (Fownes).
238 Saturated sol. of nitre boils.
221 Saturated sol. of salt boils (Paris Codex).
220 Saturated sol. of alum, carb. soda, and sulph. zinc, boil.
218 Saturated sol. of chlorate and prussiate potash, boil.
216 Saturated sol. of sulph. iron, sulph. copper, nitrate of lead, boil.
214 Saturated sol. of acetate lead, sulph. and bitartrate potash, boil.
213 or (213·5) Saturated sol. of water begins to boil in glass.
212 Water boils in metal, barometer at 30°.
211 Alloy of 5 bismuth, 3 tin, 2 lead, melts.
201 Alloy of 8 bismuth, 5 lead, 3 tin, melts (Kane).
207 Sodium melts (Regnault).
145 White of egg begins to coagulate.
185 Nitric acid 1·52 begins to boil.
180 (about) Starch forms a gelatinous compound with water.
176 Rectified spirit boils, benzol distils.
173 Alcohol (sp. gr. ·796 to ·800) boils.
151 Beeswax melts (Kane), 142 (Lepage).
150 Pyroxylic spirit boils (Scanlan).
141·8 Chloroform, and ammonia of ·945, boil.
44·5 Potassium melts (Bunsen).
132 Acetone (pyroacetic spirit) boils (Kane).
122 Mutton suet and styracin melt.
116 Bisulphuret of carbon boils (Graham).
115 Pure tallow melts (Lepage), 92 (Thomson).
112 Spermaceti and stearin of lard melt.
111 Phosphorus melts (Miller).
98 Temperature of the blood.
95 Ether (·720) boils.
95 Carbolic acid crystals become an oily liquid.
88 Acetous fermentation ceases, water boils _in vacuo_.
77 Vinous ferm. ends, acetous ferm. begins.
64·4 Oil of anise liquefies.
59 Gay Lussac’s _Alcoomètre_ graduated at.
55 Syrups to be kept at (P. L.).
30 (about) Olive oil becomes partially solid.
32 Water freezes.
·5 Cold produced by snow 2 parts and salt 1 part.
-37·9 Mercury freezes.

=TENT.= A piece of lint, or compressed sponge, used to dilate openings, wounds, &c.

=TERBIUM.= A rare metal found by Prof. Mosander, associated with erbium and yttrium in ordinary yttria. See ERBIUM and YTTRIUM.

=TER′RA.= [L.] Earth. TERRA JAPONICA, catechu; TERRA PONDEROSA, sulphate of baryta, &c.

=TER′RA COT′TA.= Literally, baked clay; a term applied to statues, architectural ornaments, &c., made of pure white clay, fine sand, and powdered potsherds, slowly dried, and baked to a strong hardness.

=TEST.= _Syn._ REAGENT. Any substance employed to determine the name or character of any other substance, or to detect its presence in compounds.

=TEST SOLUTIONS.= The test solutions here given are those of the British Pharmacopœia, which are used for determining the strength of various Pharmacopœial preparations by volumetric analysis. In the Pharmacopœia it is stated: The processes for volumetric estimations may be performed either with British or with metrical weights and measures, and the solutions are so arranged that they will be of the same strength, and the same indications will be obtained in using them, whichever system is employed, without the necessity of altering any of the figures by which the quantities of the substances tested or of the test solutions required in the process are expressed.

According to the British system, the quantities of the substances to be tested are expressed in grains by weight, whilst the quantities of the test solutions employed in testing are expressed in grain-measures, the grain-measure being the volume of a grain of distilled water.

According to the metrical system, the quantities of the substances to be tested are expressed in grammes by weight, whilst the quantities of the test solutions employed in testing are employed in cubic centimètres, the cubic centimètre being the volume of a gramme of distilled water.

As the cubic centimètre bears the same relation to the gramme that the grain-measure bears to the grain, the one system may be substituted for the other, with no difference in the results excepting that, by the metrical system, all the quantities will be expressed in relation to a weight (the gramme) which is more than fifteen times as great as the British grain.

In practice it will be found convenient in substituting metrical for British weights and measures, to reduce the values of all numbers to one-tenth by moving the decimal points, and this has been done in the tables appended to the descriptions of the volumetric solutions. The quantities indicated in the Pharmacopœia, which in grains and grain-measures can be conveniently used, would be found inconveniently large if the same numbers of grammes and cubic centimètres were employed.

The following apparatus is required in the preparation and use of these solutions.

For British weights and measures:

1. A flask, which, when filled to a mark on the neck, contains exactly 10,000 grains of distilled water at 60°. The capacity of the flask is therefore 10,000 grain-measures.

2. A graduated cylindrical jar which, when filled to O, holds 10,000 grains of distilled water, and is divided into 100 equal parts.

3. A burette. A graduated glass tube which, when filled to O, holds 1000 grains of distilled water, and is divided into 100 equal parts. Each part therefore corresponds to 10 grain-measures.

For metrical weights and measures:

1. A glass flask which, when filled to a mark on the neck, contains 1 litre, or 1000 cubic centimètres.

2. A graduated cylindrical jar which, when filled to O, contains 1 litre (1000 cubic centimètres), and is divided into 100 equal parts.

3. A burette. A graduated tube which, when filled to O, holds 100 cubic centimètres, and is divided into 100 equal parts.

(One cubic centimètre is the volume of one gramme of distilled water at 4° C.[230], 1000 cubic centimètres equal 1 litre).

[Footnote 230: It is customary to make the measurements with metrical apparatus at 60° Fahr.]

Volumetric solutions, before being used, should be shaken in order that they may be throughout of uniform strength. They should also be preserved in stoppered bottles. All measurements should be made at 60°.

VOLUMETRIC SOLUTION OF BICHROMATE OF POTASH (Bichromate of potash, KO,2CrO_{3} = 147·5, or K_{2}Cr_{2}O_{7} = 295).

Take of——
Bichromate of potash 147·5 grains.
Distilled water a sufficiency.

Put the bichromate of potash into the 10,000 grain flask, and, having half filled the flask with water, allow the salt to dissolve; then dilute the solution with more water, until it has the exact bulk of 10,000 grain-measures: 1000 grain-measures of this solution contain 14·75 grains of the bichromate (1/10th of K_{2}CrO_{3}, or 1/20th of K_{2}Cr_{2}O_{7} in grains), and, when added to a solution of a protosalt of iron, acidulated with hydrochloric acid, are capable of converting 16·8 grains (1/10th of 6Fe, or 1/20th of 6Fe in grains) from the state of protosalt to that of persalt grammes, and cubic centimètres may be employed instead of grains and grain-measures; but for convenience 1/10th of the numbers should be taken. Thus, 14·75 grammes of bichromate of potash should be made to form 1000 cubic centimètres of solution. 100 cubic centimètres of this solution contain 1·475 grammes of the bichromate (1/100th of KO,2CrO_{3}, or 1/200th of K_{2}Cr_{2}0_{7} in grammes), and, when added to a solution of protosalt of iron acidulated with hydrochloric acid, are capable of converting 1·68 grammes of iron (1/100th of 6Fe, or 1/200 of 6Fe, in grammes) from the state of protosalt to that of persalt.

This solution is used for determining the proportion of protoxide of iron in the following preparations. It is known that the whole of the protosalt has been converted into a persalt when a minute drop of the liquid, placed in contact with a solution of red prussiate of potash on a white plate, ceases to strike with it a blue colour.

British Weights Metrical Weights
and Measures. and Measures.
/-----------/\-------------\ or /---------/\--------\
Grains weight = Grain measures Grams weight = C. C. of
of substance. of vol. sol. of substance. vol. sol.

Ferri arsenias 20 = 170 or 2·0 = 17·0
” carb. sacch. 20 = 330 ” 2·0 = 33·0
” oxid. magn. 20 = 83 ” 2·0 = 8·3
” Phosphas 20 = 250 ” 2·0 = 25·0

VOLUMETRIC SOLUTION OF HYPOSULPHITE OF SODA (hyposulphite of soda crystallised, NaO_{1}S_{2}O_{2} + 5HO = 124, or Na_{2}H_{2}S_{2}O_{4}.4H_{2}0 = 248).

Take of——
Hyposulphite of soda, in crystals 280 grains.
Distilled water a sufficiency.

Dissolve the hyposulphite of soda in 10,000 grain-measures of water. Fill a burette with this solution and drop it cautiously in 1000 grain-measures of the volumetric solution of iodine until the brown colour is just discharged. Note the number of grain-measures (_n_) required to produce this effect; then put 8000 grain-measures of the same solution into a graduated jar, and augment this quantity by the addition of distilled water until it amounts to (8000 × 1000) / _n_ grain-measures. If, for example, _n_=950, the 8000 grain-measures of solution should be diluted to the bulk of (8000 × 1000) / 950 = 8·421 grain-measures. 1000 grain-measures of this solution contains 24·8 grains of the hyposulphite (1/10th of 2(NaO,S_{2}O_{2} + 5HO), or 1/10th of =Na_{2}H_{2}S_{2}O_{4},4H_{2}O= in grains), and therefore corresponds to 12·7 grains of iodine (1/10th of an equivalent).

Grammes and cubic centimètres may be employed instead of grains and grain-measures, but for convenience 1/10th of the numbers should be taken. 100 cubic centimètres of this solution contain 2·48 grammes of the hyposulphite (1/100 of 2(NaO,S_{2}O_{2}+ 5HO), or 1/100th of Na_{2}H_{2}S_{2}O_{4}.4H_{2}O in grammes), and therefore corresponds to 1·27 grains of iodine (1/100th of an equivalent).

This solution is used for testing the following substances. In each case, except that of iodine, a solution of iodide of potassium and hydrochloric acid are added to the substance, and the amount of iodine so liberated is indicated by this solution:

British Weights Metrical Weights
and Measures. and Measures.
/------------/\------------\ or /---------/\---------\
Grains weight = Grain-measures Grams weight = C. C. of
of substance. of vol. sol. of substance. vol. sol.

Calx Chlorata 10·0 = 850 or 1·00 = 85·0
Iodum 12·7 = 1000 ” 1·27 = 100·0
Liq. calc. chloratæ 60·0 = 500 ” 6·00 = 50·0
Liq. chlori 439·0 = 750 ” 43·90 = 75·0
Liq. Sodæ chloratæ 70·0 = 500 ” 7·00 = 50·0

VOLUMETRIC SOLUTION OF IODINE (iodine, I = 127, or I = 127).

Take of iodine 127 grains.
Iodide of potassium 180 ”
Distilled water a sufficiency.

Put the iodide of potassium and the iodine into the 10,000 grain flask, fill the flask to about two thirds its bulk with distilled water, gently agitate until solution is complete, and then dilute the solution with more water, until it has the exact volume of 10,000 grain-measures. 1000 grain-measures of this solution contain 1/10th of an equivalent in grains (12·7 grains) of iodine, and therefore correspond to 1·7 grains of sulphuretted hydrogen, 3·2 grains of sulphurous acid, and 4·95 grains of arsenious acid.

Grammes and cubic centimètres may be employed instead of grains and grain-measures, but for convenience 1/10th of the numbers should be taken. 100 cubic centimètres contain 1·27 grammes of iodine, and correspond to 0·17 grammes of sulphuretted hydrogen, 0·32 grammes of sulphurous, and 0·495 grammes of arsenious acid. This solution is for testing the following substances. It is dropped from the burette into the liquid to be tested, until free iodine begins to appear in the solution.

British Weights Metrical Weights
and Measures. and Measures.
/------------/\------------\ or /---------/\--------\
Grains weight = Grain-measures Grams weight = C. C. of
of substance. of vol. sol. of substance. vol. sol.

Acid. arsenios 4·0 = 808 or 0·40 = 80·8
Acid. sulphurosum 34·7 = 1000 ” 3·47 = 100·0
Liquor arsenicalis 441·5 = 808 ” 44·15 = 80·8
Liquor arsenici }
hydrochloricus} 441·5 = 810 ” 44·15 = 81·0

VOLUMETRIC SOLUTION OF NITRATE OF SILVER (nitrate of silver, AgO, NO_{5} = 170, or AgNO_{3}* = 170).

Take of nitrate of silver 170 grains.
Distilled water a sufficiency.

Put the nitrate of silver into the 10,000 grain flask, and having filled half the flask with water, allow the salt to dissolve; then dilute the solution with more water until it has the exact bulk of 10,000 grain-measures.

The solution should be kept in an opaque stoppered bottle. 1000 grain-measures of this solution contain 1/10th of an equivalent in grains of nitrate of silver (or 1·70 grains). Grammes and cubic centimètres may be employed instead of grains and grain-measures, but for convenience 1/10th of the numbers should be taken. 100 cubic centimètres contain 1/10th of an equivalent in grammes of nitrate of silver (or 1·7 grammes).

It is used in testing the following substances.

British Weights Metrical Weights
and Measures. and Measures.
/------------/\------------\ or /--------/\---------\
Grains weight = Grain-measures Grams weight = C. C. of
of substance. of vol. sol. of substance. vol. sol.

Acid. hydrocyan. 270 = 1000 or 27·0 = 100·0
Potass. bromid. 10 = 840 ” 1·0 = 84·0
Sodæ arsenias (dry) 10 = 1613 ” 1·0 = 161·3

VOLUMETRIC SOLUTION OF OXALIC ACID (crystallised oxalic acid, 2HO, C_{4}H_{6} + 4HO = 126, or H_{2}C_{2}O_{4}2H_{2}O = 126). Take of——

Purified oxalic acid in }
crystals, quite dry, but } 630 grains.
not effloresced }
Distilled water a sufficiency.

Put the oxalic acid into the 10,000 grain flask, fill the flask to about two thirds of its bulk with water, allow the acid to dissolve, and then dilute the solution with more water until it has the exact volume of 10,000 grain-measures. 1000 grain-measures of this solution contain half an equivalent in grains (63 gr.) of oxalic acid, and are therefore capable of neutralising an equivalent in grains of an alkali or alkaline carbonate. Grammes and cubic centimètres may be employed instead of grains and grain-measures, but for convenience 1/10th of the numbers should be taken. 100 cubic centimètres contain 1/20th of an equivalent in grammes (6·3 grammes) of oxalic acid, and will neutralise 1/10th of an equivalent in grammes of an alkali. The following substances are tested with this solution:

British Weights Metrical Weights
and Measures. and Measures.
/-------/\-------\ or /--------/\--------\
Grains = Grain- Grams = C. C. of
weight of measures weight of vol. sol.
substance. of vol. sol. substance.

Ammoniæ carb. 59·0 = 1000 or 5·90 = 100·0
Borax 191·0 = 1000 ” 19·10 = 100·0
Liq. ammon. 85·0 = 500 ” 8·50 = 50·0
Liq. ammon. fort. 52·3 = 1000 ” 5·23 = 100·0
Liq. calcis 4380·0 = 200 ” 438·00 = 20·0
Liq. calcis sacchar 460·2 = 254 ” 46·02 = 25·4
Liq. plumbi subacet. 413·3 = 810 ” 41·33 = 81·0
Liq. potassæ 462·9 = 482 ” 46·29 = 48·2
Liq. potassæ efferves. 4380·0 = 150 ” 438·00 = 15·0
Liq. sodæ 458·0 = 470 ” 45·80 = 47·0
Liq. sodæ efferves. 4380·0 = 178 ” 438·00 = 17·8
Plumbi acetas 38·0 = 200 ” 3·80 = 20·0
Potassa caustica 56·0 = 900 ” 5·60 = 90·0
Potassæ bicarb. 50·0 = 500 ” 5·00 = 50·0
Potassæ carb. 83·0 = 980 ” 8·30 = 98·0
Potassæ citras 102·0 = 1000 ” 10·20 = 100·0
Potassæ tartras 113·0 = 1000 ” 11·30 = 100·0
Potassæ tartras acida 188·0 = 1000 ” 18·80 = 100·0
Soda caustica 40·0 = 900 ” 4·00 = 90·0
Soda tartarata 141·0 = 1000 ” 14·10 = 100·0
Sodæ bicarb. 84·0 = 1000 ” 8·40 = 100·0
Sodæ carb. 143·0 = 960 ” 14·30 = 96·0

VOLUMETRIC SOLUTION OF SODA (hydrate of soda, NaO, HO = 40, or NaHO = 40).

Take of solution of soda a sufficiency.
Distilled water a sufficiency.

Fill a burette with the solution of soda, and cautiously drop this into 63 gr. of purified oxalic acid, dissolved in about 2 oz. of water, until the acid is exactly neutralised as indicated by litmus.

Note the number of grain-measures (_n_) of the solution used, and having then introduced 9000 grain-measures of the solution of soda in a graduated jar, augment this quantity by the addition of water until it becomes

9000 × 1000 / _n_ grain-measures =

If, for example, _n_ = 930, the 9000 grain-measures should be augmented to

9000 × 1000 / 930 = 9,677 grain-measures.

One thousand grain-measures of this solution contain one equivalent in grains (40 gr.) of hydrate of soda, and will therefore neutralise one equivalent in grains of any monobasic acid.

Grammes and cubic centimètres may be employed, instead of grains and grain-measures; but for convenience 1/10th of the numbers should be taken. 1000 cubic centimètres contain 1/10th of an equivalent in grammes (4 grammes) of hydrate of soda, and will neutralise 1/10th of an equivalent in grammes of an acid.

This solution is used for testing the following substances:

British Weights Metrical Weights
and Measures. and Measures.
/--------/\-------\ or /--------/\--------\
Grains = Grain- Grams C. C. of
weight of measures weight of = vol. sol.
substance. of vol. substance.
sol.

Acetum 445·4 = 402 or 44·54 = 40·2
Acid. acet. 182·0 = 1000 ” 18·20 = 100·0
Acid. acet. dil. 440·0 = 313 ” 44·40 = 31·3
Acid. acet. glac. 60·0 = 990 ” 6·00 = 99·0
Acid. citric 70·0 = 1000 ” 7·00 = 100·0
Acid. hydrochloric 114·8 = 1000 ” 14·48 = 100·0
Acid. hydrochloric dil. 345·0 = 1000 ” 34·50 = 100·0
Acid. nitric 90·0 = 1000 ” 9·00 = 100·0
Acid. nitric dil. 361·3 = 1000 ” 36·13 = 100·0
Acid. nitro-hydrochlor. dil. 352·4 = 920 ” 35·24 = 92·0
Acid. sulph. 50·6 = 1000 ” 5·06 = 100·0
Acid. sulph. arom. 304·2 = 830 ” 30·42 = 83·0
Acid. sulph. dil. 359·0 = 1000 ” 35·90 = 100·0
Acid. tart. 75·0 = 1000 ” 7·50 = 100·0

=TE′TANUS.= Spasm with rigidity. When it affects the under jaw, it is called TRISMUS, or locked-jaw; when the body is drawn backward by the contraction of the muscles, it is called OPISTHOTONOS; when the body is bent forward, EMPROSTHOTONOS; and when the body is drawn to one side, PLEUROSTHOTONOS.