Εικόνες σελίδας
Ηλεκτρ. έκδοση

terminating above in a sharp edge, will do). These prelimiLESSONS IN CHEMISTRY.--No. V.

naries being arranged, place under the suspended and inverted

tumbler the tobacco-pipe stem delivering hydrogen gas. If ON HYDROGEN. TÆe student will remember that in the first lesson he was told

Fig. 23. to prepare a certain combination of tobacco-pipes, corks, and large-mouthed bottles. They have not been employed hitherto, and the learner may consequently think I have forgotten ali about them: not so.

It has been my especial object to arrange these lessons in such a manner that manipulative details, or the directions for conducting-the mechanical part of operations (and chemistry is full of such), may be interspersed with a due proportion of thinking philosophy. I shall continue to hold this object in view, and therefore shall not set off the manipulative part of chemistry by itself, but describe the manufacture of every instrument when wanted.

Perhaps the operative student may have observed—at any rate, he ought to have observed, for no phenomenon occurring during the performance of a chemical operation and appertain

la) ing to it should remain unnoticed,-I say he may have observed, that during the act of solution of the zinc in dilute sulphuric acid a certain gas was evolved. Now this gas is termed hydrogen ; it is the lightest ponderable body in nature, and the common method of procuring it is really that which the the apparatus be sufficiently delicate, the tumbler t will be student has already followed, namely, by the operation of raised, thus proving the levity of hydrogen gas. There dilute sulphuric acid upon the metal zinc: iron will answer are inany processes of demonstration more elegant than this : nearly as well. Perhaps, moreover, the student may have several will he mentioned hereafter. There are none, howobserved that the hydrogen gas thus developed had a peculiar ever, of equal simplicity, as they require the use of apparatus smell; this, however, is a casualty-pure hydrogen is almost not yet described. devoid of smell. I need not describe on what the smell de- The next experiment to be mentioned shall have reference pends just at this time, further than stating that the cause is to the products of the combustion of hydrogen gas. For a sort of oil generated during the process of dissolving zinc in this purpose, ignite a jet of such gas as it emerges from dilute sulphuric acid.

the shank of the tobacco-pipe, and hold over the flame a wideLet us now learn a few properties of this gas by experiment, mouthed bottle or tumbler, as represented in the following generalising these properties hereafter. For this

diagram, fig. 24:

purpose, repeat the act of solution,--using zinc and dilute sulphuric

Fig. 24. acid as before,-only let the solution be performed in the bottle instead of an open dish, and stop its mouth with the perforated cork, armed with its tobacco-pipe shank, immediately after the zinc and dilute, acid have been poured into it. It is scarcely necessary to intimate that the mixture of sulphuric acid with the predetermined quantity of water can scarcely, with safety, be attempted in the bottle itself, on account of the heat developed. It requires to be effected in an earthenware basin, jug, cup, or something of that sort.

Having generated hydrogen in this way, we shall soon learn one of its most prominent qualities : causing a flame to approach the end of the tobacco-pipe shank, the hydrogen which escapes will immediately take fire, proving that it is combustible. In performing this experiment, it will be well for the operator to place himself at some little distance from the apparatus, because if the light be caused to approach the extremity of the tobacco-pipe shank before the generated After the lapse of a few seconds, the vessel, previously dry, will hydrogen has forced out all the atmospheric air which the be bedewed with moisture. Where does the student believe bottle originally contained, an explosion will be the result: the moisture comes from? His first idea, perhaps, might be, not dangerous in itself, but it may be destructive to the clothes that it comes from little particles blown out, as it were, from by the diffusion of the dilute acid in spray. Every pheno- the liquid in the bottle. In our rough experiment, probably menon, as I have before remarked, occurring, during the a little is attributable to that source; but if every care be taken performance of a chemical experiment is important, and should to dry the gas, still its combustion yields water--nothing but never be passed unchallenged. In the present case, we do water. Hence hydrogen derives its name from vowp, water, not stipulate for an explosion; we will effect that purposely, and yévvaw, I form; hydrogen, then, means the water.former. and by a convenient process, hereafter. Nevertheless, should If, instead of a tumbler, the student uses a large-mouthed an explosion occur, it would only serve to anticipate a com. bottle (a soda-water bottle answers remarkably well), he will munication of the fact, that hydrogen gas forms an explosive generally succeed in eliciting a roaring or singing noise, attrimixture when mingled with air in certain proportions. If butable to vibrations set up in the contained air by means of an explosion occur, replace the stopper, and wait this time the burning hydrogen. before applying the flame until all the atmospheric air has been The chemistry of gases is very delicate; I shall, therefore, expelled. This period may be readily guessed at, or may be when describing these bodies (the term sounds oddly to an uninsured, by giving the operation a little more time. Applying chemical ear, though it is correct) frequently require to mennow the flame, the jet of hydrogen will burn tranquilly, tion instruments that the student neither has nor requires to

The next experiment we will perform shall have reference have, a mere description of their form and mode of operation to the extreme lightness of hydrogen. It is this:-Attach being sufficiently instructive. Of this kind is Cavendish's to one end of a thin slip of deal, a drinking-tumbler, or Eudiometer, the instrument by which the truth that hydrogen other similar vessel, as indicated in the accompanying dia- by combustion with oxygen (for that is essential) yields water, gram at t, fig. 23, and to the other end of the same slip of deal nothing but water, was first determined. In the experiment any pan-like contrivance for the suspension of a counterpoise which we have performed, the hydrogen supplied itself with w; next, support the slip by a fulcrum f (an upright board, oxygen from the atmospheric air; but it would have been com. VOL. IT


[ocr errors]
[ocr errors]
[ocr errors]

petent for the operator to have mixed it with oxygèti previous | although not very correct in its results. The second unethod to combustion : and this is what the chemist Cavendish did. is by exhaustion, as we have seen in the instance of Cavendish's Having effected a mixture of oxygen and hydrogen, and filled Eudiometer. The third method, now to be described, is by far with this mixture a thick glass yessel

, as represented in the the most usual and most important.--collection by the pneuaccompanying diagram, fig. 26, and since known as Cavendish's / watic trough. If a bottle be taken, filled with water, and held

thus inverted over water, I need hardly say the water which it contains will not escape; but if a jet of gas be liberated under the mouth of the bottle, it follows, from a consideration of some ordinary laws of hydrostatics, that gas being lighter than water, the former will ascend and the latter will descend, until ultimately the bottle becomes quite filled with gas, but empty of water. For this elegant contrivance we are indebted to the ingenuity of Dr. Priestley. In my sketch, fig. 26, I have represented

Fig. 25.


[merged small][graphic][ocr errors]
[ocr errors]

a common basin as the ressel in which the bottle is inverted, and I have represented the bottle as supported by the hånd. I need not say this way of proceding is inconvenient; to give full effect to the operation one requires that the bottle shall stand without support, and that the vessel shall be large-one, in fact rather like a tub than a basin; a vessel thus modified becomes the pneumatic trough.

As relates to the bottle or jar in which the gas is to be collected, it will stand quite weil without any support provided its mouth be sufficiently wide; if circumstances of any kind require the use of a narrow-mouthed bottle, it may be supported in dozens of ways, readily occurring to the operator. The student need not expend one penny in the purchase of a pneumatic trough, except he has to deliver public lectures, and requires display. The first wash-bowl, kitchen-tub, foot-pan, or slop-basin he can lay hands on will answer sufficiently well; and as for the support, I will now just mention one that in many cases answers even better than a shelf. It is this.

[ocr errors]

Pig, 27.



Eudiometer, he then caused an electric discharge to traverse a pair of wires a b, penetrating the glass stopper s, so that an electric spark should pass through the space s': by this elegant contrivance the gas was ignited, and the sides of the vessel became bedewed with moisture, which on being examined was found to be water. As the experiment adverted to will scarcely be performed by any chemical novice, it would be a waste of time to describe in detail the construction and use of this beautiful instrument. I shall merely content myself, therefore, with observing that the stopper is screwed tightly down by means of a contrivance indicated in our diagram; and the foot m of brass is not permanent, but admits of being acrewed off at m', and the instrument attached to this point of į Taking a piece of tin or iron, or other metal platc, fold it into junction to the receiver of an air-pump. The student will easily understand, that the air originally contained in the vessel

Fig. 28, being pumped out, a vacuum will ensue, and the stop-cock c being screwed on to a vessel containing gas, the latter will rush in. The method here described is not the usual one by which vessels are filled with gas; chemists accomplish the object far more readily by what is called the pneumatic trough, to be described presently. In the experiment of Cavendish, however, water would have been inadmissible as the filling agent, and mercury scarcely more eligible,

Methods of Collecting Gas.---Two methods of collecting gases have already come under our notice. Firstly, we collected hydrogen by simply inverting a tumbler over a jet, through which the gas was escaping. This method is usually called that of a displacement, and is sometimes had recourse to,

[ocr errors]

the shape of a cone, the apex of which is truncated; next cut

In great concern he ran to bear the sad tidings. a notch in the lower or base edge of the cone, and the stand is The words printed in italics form an adverbial phrase. Adverbial made. The use of it will be evident from an examination of the diagram, fig. 28. The notch admits the gas delivering phrases involve what may be called an adverbial object; thus, in

be tabe, the truncated apex delivers the gas into the bottle, which great concern is an

various; as, rests supported on the sides.

If the student were not told of these contrivances he might 1. Of time: ; On arriving home I hastened to bed. think me remiss; but I want to create a feeling of independence

2. Of place:

He slew his foe in the dell. in his mind, to impress him with the conviction, that in 3. Of manner: The father begged his life with many supplications. the majority of chemical operations involving the use of mechanical contrivances, many different methods admit of

An object, then, may be not only single or compound, being followed, each equally good. The support just described Single: He launched the ship; is useful, and not inelegant, but I shall not quarrel with a Compound: The waves overwhelmed the boat and the crew; student who tells me that two bricks set edgeways in a pan of water, fig. 29, furnish a support which is nearly as good, near or remote; as,

He sold his desk;
Fig. 29.

Remote: He sold his desk to his clerk;
but also adverbial, and that of three kinds of time, of place, of

Near :



[ocr errors]

A simple sentence is a sentence which has one subject and one affirmation or predicate ; and a compound sentence is a sentence that has more than one subject and more than one predicate. The component parts of a compound sentence are called its members. These members may be two or more; they may also each form a separate sentence:

Compound Sentences of two Members. 1

2 The great fault of most books which treat of chemical ma

He will perish who loves warighteousness. nipulations is this:-they represent the apparatus which is


2 not intrinsically best for gaining any particular result, but the The lark sang his matins and sank into his nest. apparatus which makes the prettiest engraving. This, in my The first sentence is equivalent to these two propositions opinion, is but a questionable benefit to the pictorial art, and a Tast disadyantage to the student of chemistry.

1. Some one will perish.

2. The lover of unrighteousness will perish.

The second sentence is equivalent to these two statements : LESSONS IN ENGLISH-NO. LXXII.

1. The lark sang his matins.

2. The lark sank into his Dest.

Compound Sentences of three Members.


3 We have already learnt that a subject may comprise a noun or When the Queen arrived, the fleet had weighed anchor and sailed. pouns standing in apposition to the principal noun; as,

1. The Queen arrived. Principal Noun. Apposition.


2. Before then the fleet had weighed anchor. Victoria, Queen of England, conquered Burmah.

3. Before then the fileet had sailed. This appositional clause or member proves when analysed to be a Thus what in the compound sentence stands as three members, sentence of itself; e. g.,

becomes in the analysis three individual sentences.

It is easy to see that the members may be increased almost at
Victoria, who is Queen of England, conquered Burmah. pleasure :-
Similar accessaries may be made to the subject, which may be

The sick and all but dying man drinks water and revives. called

Compound sentences have members of two kinds, the principal Subject- Accessaries,

and the accessary. The principal member is that which enunciates

the leading thought, the accessary member is that which enunciates being Queen of England

the subordinate thought:
when Queen of England gained respect.
on assuming the sceptre

Principal Member.

ACCESSARY MEMBER. while Queen of England

The man drinks (and)

is refreshed. These accessaries are denominated subject accessaries, because they qualify the subject. Accessaries may qualify the object namely, interposed or appended. An accessary member is inter

The accessary member (or members) may be of two kinds,

posed when it appears in the body of a sentence, being introduced Object- Accessaries.

by a relative pronoun, a relative adverb, or a conjunction ; e, go, ( by her virtues.


Victoria gained respect for the good laws she sanctioned.

INTERPOSED. in consequence of her birth.

who drinks

is refreshed These accessaries, whether they attach to the subject or the Rel. Pron.: The man

Rel. Ad.: The man

when he drinks

is refreshed object, may be characterised as

Conjunc,: The man

if hedrinks

is refreshed Adverbial Accarsaries.

Appended members are added by means of conjunctions, The essential quality of the adverb is to declare the quality of adverbs, and pronouns:--an affirmation, thus:

He writes well.


APPENDED But the quality of an act may be assigned by an adverbial phrase conjunc.. The man drinks

and is refreshedha

Adv.: as well as by a simple adverb ; e. g.,

20hen he drinks, The man is refreshed

also; e. g.

[ocr errors]

e. g.,

The principal member may be expanded; e. g.,

The malcontents made such demands as none but a tyrant could

refuse."-Bolinbroke. Principal Member Expanded.

What is a relative which performs the double function of a subThe man drinks

ject and an object, being equivalent to that which, and used in only and is refreshed. The man eats and drinks

the neuter gender ; e. 8., The accessary member may also be expanded ; e. g.,

“My master wotteth not what is with me."-(Gen. xxxix. 8.)

As a subject for exemplifying the doctrines laid down in regard Interposed Accessary.

to the structure of sentences, I shall take some sentences from who driuks

Daniel Defoe, a writer of idiomatic English.
The man


is refreshed. who eats and drinks

Compound Sentence. The appended member, too, may be expanded ; e. g.,

“ Oxford makes by much the best outward appearance of any Appended Accessary Expanded.

city I have seen, being visible for several miles round on all sides

in a most delightful plain; and adorned with the steeples of the is refreshed.

several colleges and churches, which make a glorious show.” The man drinks (and) is refreshed and strengthened.

Here I must premise that the form "the best outward appearSentences may be further divided into the direct and the inverted. ance of any city,” &c., is incorrect, and should have been the A sentence is direct when the principal member precedes the best outward appearance of all the cities I," &c. This compound

sentence may be reduced into these simple sentences :accessary; e. g.,

1. Oxford makes a very good appearance. Direct Sentence.

2. Oxford makes an appearance better than many cities. Principal.


3. I have never seen a city with a better appearance than The man drinks (and) is refreshed.


4. Oxford is visible for several miles round. A sentence is inverted when the accessary sentence precedes the

5. Oxford is visible from all sides. principal:

6. Oxford stands in a most delightful plain.

. Inverted Sentence.

7. Oxford is adorned with the steeples of several colleges.

8. Oxford is adorned with the steeples of several churches. Accessary. Principal.

9. The architectural decorations of Oxford make a glorious show. if he drinks. The man is refreshed when he drinks.

The resolution of this long sentence into the several distinct should he drink.

propositions which it contains, has, by showing the meaning of the

several parts, prepared the way for our exhibiting the logical relaRelative pronouns are such pronouns as relate to some pre- tions which those parts sustain to each other, thus :ceding noun, called the antecedent ; that is, the foregoing word;

Logical Relations of the Sentence.
Relatives and Antecedents,

1. Oxford

the subject to 2

2. makes

makes together with 3 the predi

cate to 1 Subject. The man who drinks water is wise.

3. the best outward appearance the object to 2 Object. The men whom he met he struck. 4. of any city

adverbial object to 2

appended accessary to 2 The relative must agree with its antecedent in person, gender, 5. that I have seen and number; e. g.,

6. being visible

accessary to the subject 1

7. for several miles round adverbial object to 6


8. on all sides

9. in a most delightful plain
1. I

10. and adorned

second accessary to 1
2 He


11, with the steeples, &c. adverbial object to 10 In number one, who is of the first person, because I is of the 12. which makes a glorious ehow appended accessary to 10 first person ; who is of the singular number, because I is of the Several of these parts may be analysed or explained ; e. &., singular number. The effect of the relative on the verb is more Number three consists of the definite article the, the superlative clearly seen in the second instance, where an s is added to the verb, adjective best, the adjective outward in the positive degree, and which accordingly appears as reflects.

the common noun appearance, which is the object to the verb

makes, As the language is now written and spoken by the best authori. ties, the relative who has one change of form in the nominative, Number six presents a case of explanatory apposition, since namely, in which ; which is commonly applied to things. Who, being visible is subjoined to the subject Oxford in order to state however, has a genitive and an objective, as well as a nominative some additional facts respecting it; number ten stands to numcase, and may be declined or inflected thus :

ber one in the same relation.

Number twelve presents an appended relative accessary sentence WHO DECLINED.

of which these are the components ; namely, which, a relative pro

noun agreeing with its antecedent steeples ; make, a verb in the Singular and Plural. Masculine. Feminine. Neuter

indicative mood, third person, plural number, agreeing with its SINGULAR Nom. who


which subject which; a, the indefinite article limiting show; glorious, an Genit. whose

whose of which (whose) adjective qualifying show; show, a common noun dependent on PLURAL. . ) Object. whom

whom which

or the object to the verb make, Viewed structurally, this Instead of whose and which we sometimes find whereof.

appendage stands thus :

That, which is without any inflexional change, may be used

Verb." in lieu of who or which, being applied to both persons and


Which things; e. g.,

make a glorious show. “ He that reproacheth a scorner, getteth to himself shame."- By way of applying what you have learnt, take portions of any (Prov. ix 7.

good prose author, mark the logical relations of the sentences The word as is also used with the force of a relative after such, after you have resolved each into the simple propositions of which to many, the same; C. g.,

it consists, and explain by grammatical analysis (that is, "parse")

[ocr errors]


« ΠροηγούμενηΣυνέχεια »