Chapter II: Part 2

You must then add together the 1st, 3d, and 5th sums, viz., 10 + 24 + 20 = 54, and the 2d and 4th, 15 + 31 = 46; take one from the other, leaving 8. The half of this is the first number, 4; if you take this from the sum of the 1st and 2d you will have the 2d number, 6; this taken from the sum of the 2d and 3d will give you the 3d, 9; and so on for the other numbers.

THIRD CASE.

Where one or more of the numbers are 10, or more than 10, and where an even number of numbers has been thought of.

Suppose he fixes on six numbers, viz: 2, 6, 7, 15, 16, 18. He must add together the numbers as follows, and tell you the sum in each case:

1. The sum of the 1st and 2d 8
2. The sum of the 2d and 3d 13
3. The sum of the 3d and 4th 22
4. The sum of the 4th and 5th 31
5. The sum of the 5th and 6th 34
6. The sum of the 2d and last 24

You must then add together the 2d, 4th, and 6th sums, 13 + 31 + 24 = 68, and the 3d and 5th sums, 22 + 34 = 56. Subtract one from the other, leaving 12; the 2d number will be 6, the half of this; take the 2d from the sum of the 1st and 2d, and you will get the 1st; take the 2d from the sum of the 2d and 3d, and you will have the 3d, and so on.

How Many Counters Have I in My Hands?

A person having an equal number of counters in each hand, it is required to find how many he has altogether.

Suppose he has 16 counters, or 8 in each hand. Desire him to transfer from one hand to the other a certain number of them, and to tell you the number so transferred. Suppose it be 4, the hands now contain 4 and 12. Ask him how many times the smaller number is contained in the larger; in this case it is three times. You must then multiply the number transferred, 4, by the 3, making 12, and add the 4, making 16; then divide 16 by the 3 minus 1; this will bring 8, the number in each hand.

In most cases fractions will occur in the process; when 10 counters are in each hand and if four be transferred, the hands will contain 6 and 14.

He will divide 14 by 6 and inform you that the quotient is 2-1/3.

You multiply 4 by 2-1/3, which is 9-1/3.

Add four to this, making 13-1/3 equal to 40/3.

Subtract 1 from 2-1/3, leaving 1-1/3 or 4/3.

Divide 40/3 by 4/3, giving 10, the number in each hand.

The Three Travelers.

Three men met at a caravansary or inn, in Persia; and two of them brought their provisions along with them, according to the custom of the country; but the third, not having provided any, proposed to the others that they should eat together, and he would pay the value of his proportion. This being agreed to, A produced 5 loaves, and B 3 loaves, all of which the travelers ate together, and C paid 8 pieces of money as the value of his share, with which the others were satisfied, but quarreled about the division of it. Upon this the matter was referred to the judge, who decided impartially. What was his decision?

At first sight it would seem that the money should be divided according to the bread furnished; but we must consider that as the 3 ate 8 loaves, each one ate 2-2/3 loaves of the bread he furnished. This from 5 would leave 2-1/3 loaves furnished the stranger by A; and 3 - 2-2/3 = 1/3 furnished by B, hence 2-1/3 to 1/3 = 7 to 1, is the ratio in which the money is to be divided. If you imagine A and B to furnish, and C to consume all, then the division will be according to amounts furnished.

The Money Game.

A person having in one hand a piece of gold, and in the other a piece of silver, you may tell in which hand he has the gold, and in which the silver, by the following method: Some value, represented by an even number, such as 8, must be assigned to the gold; and a value represented by an odd number, such as 3, must be assigned to the silver; after which, desire the person to multiply the number in the right hand by any even number whatever, such as 2, and that in the left by an odd number, as 3; then bid him add together the two products, and if the whole sum be odd, the gold will be in the right hand, and the silver in the left; if the sum be even, the contrary will be the case.

To conceal the artifice better, it will be sufficient to ask whether the sum of the two products can be halved without a remainder, for in that case the total will be even, and in the contrary case odd.

It may be readily seen that the pieces, instead of being in the two hands of the same person, may be supposed to be in the hands of two persons, one of whom has the even number, or piece of gold, and the other the odd number, or piece of silver. The same operations may then be performed in regard to these two persons, as are performed in regard to the two hands of the same person, calling the one privately the right, and the other the left.

The Philosopher’s Pupils.

To find a number of which the half, fourth, and seventh, added to three, shall be equal to itself.

This was a favorite problem among the ancient Grecian arithmeticians, who stated the question in the following manner: “Tell us, illustrious Pythagoras, how many pupils frequent thy school?” “One-half,” replied the philosopher, “study mathematics, one-fourth natural philosophy, one-seventh preserve silence, and there are three females besides.”

The answer is 28: 14 + 7 + 4 + 3 = 28.

The Certain Game.

Two persons agree to take, alternately, numbers less than a given figure, for example, 11, and to add them together till one of them has reached a certain sum, such as 100. By what means can one of them infallibly attain to that number before the other?

The whole artifice in this consists in immediately making choice of the numbers, 1, 12, 23, 34, and so on, or of a series which continually increases by 11, up to 100. Let us suppose that the first person, who knows the game, makes choice of 1, it is evident that his adversary, as he must count less than 11, can at most reach 11, by adding 10 to it. The first will then take 1, which will make 12; and whatever number the second may add, the first will certainly win, provided he continually add the number which forms the complement of that of his adversary to 11; that is to say, if the latter take 8, he must take 3; if 9, he must take 2; and so on. By following this method, he will infallibly attain to 89, and it will then be impossible for the second to prevent him from getting first to 100; for whatever number the second takes he can attain only to 99; after which the first may say--“and 1 makes 100.” If the second take 1 after 89, it would make 90, and his adversary would finish by saying--“and 10 make 100.” Between two persons who are equally acquainted with the game, he who begins must necessarily win.

The Dice Guessed Unseen.

A pair of dice being thrown, to find the number of points on each die without seeing them. Tell the person who cast the dice to double the number of points upon one of them, and add 5 to it; then to multiply the sum produced by 5, and to add to the product the number of points upon the other die. This being done, desire him to tell you the amount, and having thrown out 25, the remainder will be a number consisting of two figures, the first of which, to the left, is the number of points on the first die, and the second figure, to the right, the number of the other. Thus:

Suppose the number of points of the first die which comes up to be 2, and that of the other 3; then, if to 4, the double of the points of the first, there be added 5, and the sum produced, 9, be multiplied by 5, the product will be 45; to which, if 3, the number of points on the other die, be added, 48 will be produced, from which, if 25 be subtracted, 23 will remain; the first figure of which is 2, the number of points on the first die, and the second figure 3, the number on the other.

The Famous Forty-five.

How can number 45 be divided into four such parts that, if to the first part you add 2, from the second part you subtract 2, the third part you multiply by 2, and the fourth part you divide by 2, the sum of the addition, the remainder of the subtraction, the product of the multiplication, and the quotient of the division, be all equal?

The first is 8; to which add 2, the sum is 10
The second is 12; subtract 2, the remainder is 10
The third is 5; multiplied by 2, the product is 10
The fourth is 20; divided by 2, the quotient is 10
--
45

Required to subtract 45 from 45, and leave 45 as a remainder.

SOLUTION.--9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1 = 45.
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 = 45.
--------------------------------------
8 + 6 + 4 + 1 + 9 + 7 + 5 + 3 + 2 = 45.

The Astonished Farmer.

A and B took each 30 pigs to market. A sold his at 3 for a dollar, B at 2 for a dollar, and together they received $25. A afterwards took 60 alone, which he sold as before, at 5 for $2, and received but $24: what became of the other dollar?

This is rather a catch question, the insinuation that the first lot were sold at the rate of 5 for $2, being only true in part. They commence selling at that rate, but after making ten sales, A’s pigs are exhausted, and they have received $20; B still has 10, which he sells at “two for a dollar,” and of course receives $5; whereas had he sold them at the rate of 5 for $2, he would have received but $4. Hence the difficulty is easily settled.

The Expunged Figure.

In the first place we desire a person to write down secretly, in a line, any number of figures he may choose, and add them together as units; having done this, tell him to subtract that sum from the line of figures originally set down; then desire him to strike out any figure he pleases, and add the remaining figures in the line together as units (as in the first instance), and inform you of the result, when you will tell him the figure he has struck out.

76542 -24
24
-----
76518

Suppose, for example, the figures put down are 76542; these added together, as units, make a total of 24; deduct twenty-four from the first line, and 76518 remain; if 5, the center figure, be struck out, the total will be 22. If 8, the first figure, be struck out, 19 will be the total.

In order to ascertain which figure has been struck out, you make a mental sum one multiple of 9 higher than the total given. If 22 be given as the total, then 3 times 9 are 27, and 22 from 27 show that 5 was struck. If 19 be given, that sum deducted from 27 shows 8.

Should the total be equal multiples of 9, as 18, 27, 36, then 9 has been expunged.

With very little practice, any person may perform this with rapidity: it is therefore needless to give any further examples. The only way in which a person can fail in solving this riddle is when either a number 9 or a 0 is struck out, as it then becomes impossible to tell which of the two it is, the sum of the figures in the line being an even number of nines in both cases.

Mysterious Addition.

It is required to name the quotient of five or three lines of figures--each line consisting of five or more figures--only seeing the first line before the other lines are even put down. Any person may write down the first line of figures for you. How do you find the quotient?

86,214
42,680
57,319
62,854
37,145
------
286,212

When the first line of figures is set down, subtract 2 from the last right-hand figure, and place it before the first figure of the line, and that is the quotient for five lines. For example, suppose the figures are 86,214, the quotient will be 286,212. You may allow any person to put down the two first and the fourth lines, but you must always set down the third and fifth lines, and in doing so always make up 9 with the line above.

Therefore in the annexed diagram you will see that you have made 9 in the third and fifth lines with the lines above them. If the person you request to put down the figures should set down a 1 or 0 for the last figure, you must say: “We will have another figure,” and another, and so on until he sets down something above 1 or 2.

67,856
47,218
52,781
------
167,855

In solving the puzzle with 3 lines, you subtract 1 from the last figure, and place it before the first figure, and make up the third line yourself to 9. For example: 67,856 is given, and the quotient will be 167,855, as shown in the above diagram.

The Remainder.

A very pleasing way to arrive at an arithmetical sum, without the use of either slate or pencil, is to ask a person to think of a figure, then to double it, then add a certain figure to it, now halve the whole sum, and finally to abstract from that the figure first thought of. You are then to tell the thinker what is the remainder.

The key to this lock of figures is, that _half_ of whatever sum you request to be added during the working of the sum _is the remainder_. In the example given, 5 is the half of 10, the number requested to be added. Any amount may be added, but the operation is simplified by giving only even numbers, as they will divide without fractions.

Think of 7
Double it 14
Add 10 to it 10
--
Halve it 2 ) 24
--
Which will leave 12
Subtract the number thought of 7
--
_The remainder_ will be 5

The Three Jealous Husbands.

Three jealous husbands, A, B and C, with their wives being ready to pass by night over a river, find at the water-side a boat which can carry but two at a time, and for want of a waterman they are compelled to row themselves over the river at several times. The question is, how those six persons shall pass, two at a time, so that none of the three wives may be found in the company of one or two men, unless her husband be present?

This may be effected in two or three ways; the following may be as good as any: Let A and wife go over--let A return--let B’s and C’s wives go over--A’s wife returns--B and C go over--B and wife return, A and B go over--C’s wife returns, and A’s and B’s wives go over--then C comes back for his wife. Simple as this question may appear, it is found in the works of Alcuin, who flourished a thousand years ago, hundreds of years before the art of printing was invented.

The Arithmetical Mouse-Trap.

One of the best and most simple mouse-traps in use may be constructed as follows: Get a slip of smooth pine, about the eighth of an inch thick, a quarter of an inch broad, and of sufficient length to cut out the following parts of a trap: First, an upright piece, three or four inches high, which must be square at the bottom, and a small piece to be cut off at the top to fit a notch in No. 2.

The second piece must be of the same length as the first, with the notch cut across nearly at the top of it, to fit the top of No. 1, and the other end of it trimmed to catch the notch in No. 3. The third piece should be twice as long as either of the others; a notch, similar to that in No. 2, must be cut in one end of it to catch the lower end of No. 2. Having proceeded thus far, you must put the pieces together, in order to finish it, by adding another notch in No. 3, the exact situation of which you will discover as follows: Place No. 1 upright, then put the notch of No. 2 in the thinned top of No. 1; then get a flat piece of wood, or a slate, one end of which must rest on the ground, and the center of the edge of the other on the top of No. 2. You will now find the thinned end of No. 2 elevated by the weight of the flat piece of wood or slate; then put the thinned end of it in the notch of No. 3, and draw No. 2 down by it, until the whole forms a resemblance of a figure 4; at the exact place where No. 3 touches the upright, cut a notch, which, by catching the end of No. 1, will keep the trap together. You may now bait the end of No. 3 with pieces of cheese; a mouse, by nibbling the bait, will pull down No. 3, the other pieces immediately separate, and the slate or board falls upon the mouse. We have seen numbers of mice, rats and birds caught by this.

HOW TO BECOME A CHEMIST.

In the eleventh century, and during the reign of King Henry the First, surnamed Beauclerk, or the fine scholar, there appeared for the first time in certain books, professing to teach the art of making gold, the words chemistry, chemist, derived from the Greek. Seven hundred years and more have passed away, and that which was only the pursuit of a shadow called alchemy, has resulted in the acquisition of a great and noble science, now and again called chemistry. So it is with the great edifice Chemistry; we may, in these brief pages, peep in at the open door, but should we desire to go beyond the threshold, there are numerous guides, such as Roscoe, Wilson, and Fownes, who will conduct us through the mazes of the interior, and explain in elementary language the beautiful processes which have become so useful to mankind.

Chemistry is one of the most comprehensive of all the sciences, and at the same time one which comes home to us in the most ordinary of our daily avocations. Most of the arts of life are indebted to it for their very existence, and nearly all have been, from time to time, improved by the application of its principles.

Chemistry is, in fact, the science which treats of the composition of all material bodies, and of the means of forming them into new combinations, and reducing them to their _ultimate elements_, as they are termed; that is, bodies which we are unable to split up, as it were, or separate into other bodies. To take a common substance as an illustration; water, by a great number of processes, can be separated into two other substances, called oxygen and hydrogen, in the proportion by weight of 8 parts of the first to 1 of the second; but no power that we at present possess can separate the oxygen and hydrogen into any other bodies; they are therefore called ultimate elements, or undecomposable bodies.

Again, sulphate of magnesia (common Epsom salts) can be very easily separated into two other substances,--sulphuric acid and magnesia; and in this instance, both these substances can again be subdivided--the acid into sulphur and oxygen, and the magnesia into a metallic body called magnesium and oxygen; but sulphur, oxygen, and magnesium are incapable of further division, and are therefore called _ultimate elements_.

These ultimate elements amount to 64 in number, according to the present state of our knowledge, and may be arranged in various ways; the simplest plan, perhaps, is dividing them into Non-metallic and Metallic elements.

The Non-metallic elements are:--1. Oxygen. 2. Hydrogen. 3. Nitrogen. 4. Chlorine. 5. Iodine. 6. Bromine. 7. Fluorine. 8. Carbon. 9. Sulphur. 10. Selenium. 11. Tellurium. 12. Silicon. 13. Boron. 14. Phosphorus. The last-named element is the connecting link with the metals through arsenic, which phosphorus closely resembles in its chemical properties.

The Metallic elements may be sub-divided into the metals of the alkalies, the metals of the alkaline earths, the metals of the earths, and the other metals sometimes called metals proper.

1st. The metallic bases of the alkalies:--potassium, sodium, lithium, ammonium, cæsium, rubidium.

2d. The metallic bases of the alkaline earths:--calcium, strontium, barium.

3d. The metallic bases of the earths:--aluminum, glucinum, zirconium, thorium, yttrium, erbium, cerium, lanthanum, didymium.

4th. The metals proper, the most important of which are:--platinum, gold, silver, mercury, copper, iron, tin, lead, nickel, zinc, bismuth, antimony, manganese, cobalt, arsenic.

Now, from these elementary bodies, united together in various proportions, is formed the infinite variety of substances around us, whether animal, vegetable, or mineral; in fact, a few only are generally employed:--in the case of animals and vegetables, oxygen, hydrogen, carbon, nitrogen, with occasionally some sulphur, calcium, phosphorus, and silicon, suffice for building up the beautiful forms of animated nature; while the fabric of our globe itself consists for the most part of the earths; silex, _i.e._, flint or crystal; lime, in the shape of chalk, marble, or limestone, such as our flagstones are composed of; slate and granite, which are compounds of aluminium, silica, and small quantities of oxide of iron, and sometimes a little potash, etc.; and through their masses are projected irregular streams--veins as they are termed--of the metals, either in a pure state, as is the case sometimes with gold, silver, platinum, mercury, and perhaps one or two others; or combined with one of the non-metallic elements, or with one another.

Late calculations have determined the composition of the earth’s solid crust in 100 parts by weight to be:

Oxygen 44.0 to 48.7.
Silicon 22.8 “ 36.2.
Aluminium 9.9 “ 6.1.
Iron 9.9 “ 2.4.
Calcium 6.6 “ 0.9.
Magnesium 2.7 “ 0.1.
Sodium 2.4 “ 2.5.
Potassium 1.7 “ 3.1.
------ ------
100.0 100.0
------ ------

All these combinations are effected by certain powers, termed _forces_; those which cause the union of the elements are called the forces of attraction; those causing their separation, the forces of repulsion.

The force of attraction when exerted between masses of matter, is termed gravitation; when it unites particles of matter of a similar kind and produces masses, it is called the attraction of cohesion; when the particles united are of a dissimilar character, it is then termed chemical or elective affinity. For example, the crystals of Epsom salts are formed from minute particles of the salt, united into a larger or smaller mass by the attraction of cohesion, while the _elements_ of which each particle consists, namely, the sulphur, oxygen, and magnesium, are united by the attraction of chemical affinity.

Cohesion thus unites particles of a similar kind; chemical affinity, of a dissimilar nature. It is to cohesion that the existence of _masses_ of matter is owing, and its power increases as the squares of the distances diminish, in an inverse ratio to the squares of the distances of the particles on which it acts.

The power exerted by cohesion may be exhibited in various ways. This is one: Procure two discs of glass about three inches in diameter, their surfaces being ground extremely smooth; fix each into a square piece of wood, taking care that they are placed accurately in the center; then put them together by sliding their edges very carefully over each other, so as to avoid any air getting between them, and you will find a great force necessary to separate them. A hook should be fixed into the center of each piece of wood, so that they may be suspended, and a weight hung to the lower one. It is almost impossible for any one to separate them by merely pulling them with both hands; a weight of many pounds is required for that purpose. In like manner two freshly-cut surfaces of caoutchouc will, on being squeezed together, cohere so perfectly, that it is difficult to tear them asunder, and it is in this way that tubes of caoutchouc may be rapidly prepared for experiments, where little or no pressure is exerted.

Chemical affinity is sometimes called _elective_, or the effect of _choice_, as if one substance exerted a kind of _preference_ for another, and chose to be united to it rather than to that with which it was previously combined; thus, if you pour some vinegar, which is a weak acetic acid, upon some pearlash (a combination of potash and carbonic acid), or some carbonate of soda (a combination of the same acid with soda), a violent effervescence will take place, occasioned by the escape of the carbonic acid, displaced in consequence of the potash or soda preferring the acetic acid, and forming a compound called an acetate. Then if some sulphuric acid be poured on this new compound, the acetic acid will in its turn be displaced by the greater attachment of either of the bases, as they are termed, for the sulphuric acid. Again, if into a solution of blue vitriol (a combination of sulphuric acid with oxide of copper) the bright blade of a knife be introduced, the knife will speedily be covered with a coat of copper, deposited in consequence of the acid _preferring_ the iron, of which the knife is made, a quantity of it being dissolved in exact proportion to the quantity of copper deposited.

It is on the same principle that a very beautiful preparation called a silver-tree, or a lead-tree, may be formed thus:--Fill a wide bottle, capable of holding from half a pint to a pint, with a tolerably strong solution of nitrate of silver (lunar caustic), or acetate of lead, in pure distilled water; then attach a small piece of zinc by a string to the cork or stopper of the bottle, so that the zinc shall hang about the middle of the bottle, and set it by where it may be quite undisturbed; in a short time, brilliant plates of silver or lead, as the case may be, will be seen to collect around the piece of zinc, assuming more or less of the crystalline form. This at first is a case of elective affinity; the acid with which the silver or lead was united _prefers_ the zinc to either of those metals, and in consequence discards them in order to attach the zinc to itself, subsequently a voltaic current is set up between the two metals, and the process will continue until almost the whole of the zinc is taken up, or nearly the whole of the silver or lead deposited.

Again, many animal and vegetable substances consist for the most part of carbon or charcoal, united with oxygen and hydrogen in the proportion which forms water. Now oil of vitriol (strong sulphuric acid) has so powerful an affinity, or so great a _thirst_ for water, that it will abstract it from almost any body in which it exists; if you then pour some of this acid on a lump of sugar, or place a chip of wood in it, the sugar or wood will speedily become quite black, or be _charred_, as it is called, in consequence of the oxygen and hydrogen being removed by the sulphuric acid, and only the carbon, or charcoal, left.

When Cleopatra dissolved pearls of wondrous value in vinegar, she was exhibiting unwittingly an instance of chemical elective affinity; the pearl being simply carbonate of lime, which was decomposed by the greater affinity or fondness of lime for its new acquaintance (the acetic acid of the vinegar) than for the carbonic acid, with which it had been united all its life,--an example of inconstancy in strong contrast with the conduct of its owner, who chose death rather than become the mistress of her lover’s conqueror.

Gases.

The three permanent gaseous elements are oxygen, hydrogen, and nitrogen.

The compound gases are very numerous, some being combustible, and others supporters of combustion.

Gases are for the most part transparent and colorless, with a few exceptions, and of course, like the air of the atmosphere, invisible. They are little affected by the attraction of cohesion, but rather, on the contrary, the particles composing them have a constant tendency to separate from each other, so that their force of expansion is only limited by the pressure under which they may be kept, and the temperature they may be exposed to. They have a tendency to _penetrate_ each other, as it were; for instance, if you take a jar of heavy gas, such as carbonic gas, set it with its mouth upwards, then invert over it another jar containing hydrogen, a gas nearly twenty-two times lighter, in a very short time the two gases will have become thoroughly mixed, the heavy carbonic acid having risen, and the light hydrogen fallen, until the gases are thoroughly mixed, each jar containing an equal quantity of each gas.

Oxygen Gas.

This gas, so named from two Greek words signifying the maker of acid, was discovered by Dr. Priestly in 1774. He obtained it by heating the red oxide of mercury in a glass retort, when the gas escaped in considerable quantities. In the ensuing year Scheele obtained it by a variety of methods, and a few years afterwards Lavoisier discovered that it was contained in atmospheric air, where it exists in the proportion of about one-fifth, the remaining four fifths being almost entirely nitrogen.

Oxygen gas may be obtained for the purpose of experiment, by heating to redness the black oxide of manganese in an iron bottle, to the mouth of which a flexible tube is attached to convey away the gas as fast as it is liberated from the manganese. The first portions should be allowed to escape, being mixed with the air in the tubes and bottle, and the remainder may be collected in a gasometer, or in glass jars inverted over water.

Another method to obtain the gas, and one to be used only in the absence of other ingredients, is to mix in a retort some of this same oxide of manganese with about half its weight of strong sulphuric acid, and apply heat to the retort, when the gas will come over in considerable quantities; the first portions must be allowed to escape as before.[1] If the gas is required very pure, a small quantity of the salt called chlorate of potassa, may be heated in a retort, and oxygen gas will be evolved, and may be collected as before. If you have an iron bottle, the first mode is by far the cheapest, as the heat of a bright fire is sufficient for the operation, and a large quantity of gas is obtained in a short time from a very inexpensive material. The most rapid and convenient process of all is to heat a mixture of two parts chlorate of potash, and one of powdered black oxide of manganese, in a common clean oil flask, to which a cork and bent tube has been adapted. Care must be taken not to mistake sulphide of antimony for black oxide of manganese, as very serious accidents have arisen from this cause.

Oxygen is largely distributed over our globe, both in its uncombined state, and in union with other substances. Besides forming one-fifth of the atmosphere, it forms eight-ninths by weight of all the water in the ocean, rivers, and springs on the face of the whole earth. It also, in combination with various metals, forms the various earths and minerals of which the crust of the earth consists, so that it is the most abundant and widely distributed substance in nature, and in combination with other elements, forms nearly half the weight of the solid earth.

In its uncombined state it is a colorless gas, somewhat heavier than atmospheric air, without taste or smell. It is a powerful supporter of combustion, and is absolutely necessary for the support of animal life, which cannot exist for any time without a free supply of this gas, which is constantly consumed in the act of breathing and is replaced by an equivalent portion of carbonic acid gas. The want of oxygen is partly the cause of the oppression felt in crowded rooms, where the air cannot be renewed so fast as is required for the number of persons who are constantly consuming the oxygen; and if an animal be confined under a glass jar inverted over water, it will presently die, just for the same reason that burning tapers are extinguished under similar circumstances.

If a jet of this gas be thrown upon a piece of charcoal, sulphur, or almost any combustible body in a state of ignition, it will make it burn with great vividness and rapidity.

FOOTNOTE:

[1] Some _boiling_ water should be added to the mass left in the retort directly the gas has ceased to come away, or it will adhere to the glass so firmly, that the retort will certainly be spoilt.

Experiment.

But by far the most intense heat, and most brilliant light, may be produced by introducing a piece of phosphorus into a jar of oxygen. The phosphorus may be placed in a small copper cup, with a long handle of thick wire passing through a hole in a cork that fits the jar. The phosphorus must first be ignited; and, as soon as it is introduced into the oxygen, it gives out a light so brilliant that no eye can bear it, and the whole jar appears filled with an intensely luminous atmosphere. It is well to dilute the oxygen with about one-fourth part of common air to moderate the intense heat which is nearly certain to break the jar if pure oxygen is used.

Experiment.

If a piece of charcoal, which is pure carbon or nearly so, be ignited, and introduced into a jar containing oxygen or common atmospheric air, the product will be carbonic gas only, of which we shall speak presently. As most combustible bodies contain both carbon and hydrogen, the result of their combination is carbonic acid and water. This is the case with the gas used for illumination; and in order to prevent the water so produced from spoiling goods in shops, various plans have been devised for carrying off the water when in the state of steam. This is generally accomplished by suspending over the burners glass bells, communicating with tubes opening into the chimney, or passing outside the house.

To show that oxygen, or some equivalent, is necessary for the support of combustion, fix two or three pieces of wax-taper on flat pieces of cork, and set them floating on water in a soup-plate, light them, and invert over them a glass jar; as they burn, the heat produced may perhaps at first expand the air so as to force a small quantity out of the jar, but the water will soon rise in the jar, and continue to do so until the tapers expire, when you will find that a considerable portion of the air has disappeared, and what remains will no longer support flame; that is, the oxygen has been converted partly into water, and partly into carbonic acid gas, by uniting with the carbon and hydrogen, of which the taper consists, and the remaining air is principally nitrogen, with some carbonic acid; the presence of the latter may be proved by decanting some of the remaining air into a bottle, and then shaking some lime-water with it, which will absorb the carbonic acid and form chalk, rendering the water quite turbid.

Nitrogen.

This gas is, as its name implies, the producer of niter, or at least forms a portion of the nitric acid contained in niter. It is rather lighter than atmospheric air, colorless, transparent, incapable of supporting animal life, on which account it is sometimes called azote--an objectionable name, as it is not a poison like many other gases, but destroys life only in the absence of oxygen. This gas extinguishes all burning bodies plunged into it, and does not itself burn. It exists largely in nature, for four-fifths of the atmosphere consists of nitrogen gas. It is also an important constituent of animal bodies, and is found in the vegetable world.

Nitrogen may be most easily obtained for experiment by setting fire to some phosphorus contained in a porcelain or metallic cup, placed under a gas jar full of air, and resting on the shelf of the pneumatic trough, or in a soup-plate filled with water.

Nitrogen combines in five different proportions with oxygen producing five distinct chemical compounds, named respectively nitrous oxide, nitric oxide, nitric tri-oxide, nitric tetroxide, nitric pent-oxide, which last, united with water, forms nitric acid, now called hydric nitrate, as nitrous acid is termed hydric nitrite.

Nitrous oxide gas is generally known by the name of “laughing gas,” from the jolly sensations experienced on inhaling it. It may be procured by distilling in a glass retort a salt called nitrate of ammonia, which yields the gas in considerable quantities, and it should be kept standing in jars over water for some hours before it is used. It should be transferred into a silk air-tight bag, furnished with a stop-cock and mouth-piece, from which the gas may be breathed; a little practice is required to do this easily, and more resolution to desist when the gas begins to produce its effects, as it appears to fascinate the experimenter, and actual force is often necessary to remove the bag from the mouth. The effects produced vary according to the temperament of the person inhaling it; they are, however, always of a highly pleasurable nature, muscular action being generally greatly exalted, compelling the individual to race round the apartment and execute leaps and pirouettes perfectly astounding. Some persons shout and sing, and I have seen one expend his superfluous animation in twisting his features into such ludicrous grimaces as would be the envy of the candidates at a grinning match, and beat them all out of the field.

This gas is heavier than air, and supports combustion nearly as energetically as oxygen, as may be shown by introducing a piece of ignited phosphorus into a jar of this gas. It will not, however, support the life of small animals, such as mice, which introduced into it die very quickly.

The next compound of nitrogen with oxygen, when one proportion of nitrogen unites with two of oxygen, is termed nit_ric_ oxide gas. It may be easily procured by heating in a retort some copper turnings in dilute nitric acid. It is colorless and transparent, and has the property of combining with oxygen to form other compounds.

Experiment.

Into a jar of this gas standing over water pass some oxygen gas. The jar will be filled with red fumes, which will be rapidly absorbed by the water. If atmospheric air be used instead of oxygen, there will remain in the jar the nitrogen of the air amounting to four-fifths of the air employed.

This gas is destructive to animal life, in consequence of its property of uniting with the oxygen in the lungs, and producing the highly corrosive nitrous acid gas. It will, however, support the combustion of a few substances, phosphorus for instance, provided it is sufficiently heated before being plunged into the gas.

We pass over the third and fourth compounds of nitrogen with oxygen, as they are not calculated for amusing experiments. Nitric acid is easily prepared on the small scale, by gradually heating equal parts by weight of nitric and sulphuric acid in a retort to which a receiver has been adapted. The receiver, which may be a clean oil flask, should be kept cool with wetted blotting paper.

Nitrogen combines with chlorine and iodine, forming detonating compounds, the former being so extremely dangerous that it will be better to pass it by.

The compound with iodine, called iodide of nitrogen, may very easily be made by pouring a strong solution of ammonia (a compound of nitrogen and hydrogen) upon some iodine in a vial, shaking them well together, and after letting them stand for a few hours, pouring off the fluid; the black powder remaining in the vial is the explosive compound, the iodide of nitrogen. When dry, it is very apt to detonate spontaneously; it should therefore be shaken out of the vial while _wet_, and spread in very small quantities on separate pieces of blotting paper, which should be kept apart from each other. When thoroughly dry, the slightest touch with the point of a feather, shaking the paper on which it rests, or even opening too rapidly the door of a closet where it has been put to dry, will cause it to explode, producing a quantity of violet-colored fumes. The explosion is somewhat violent, producing a sharp cracking noise; and the greatest care should be taken in experimenting with it.

Atmospheric Air.

As has been already mentioned, nitrogen is the principal constituent of the air of the atmosphere which surrounds our globe, extending to a height of about forty-five miles above it, and playing a most important part in the economy of nature, inorganic as well as organic.

This atmospheric air consists by volume of nearly four-fifths of nitrogen, and rather more than one-fifth of oxygen, viz.: seventy-nine of the former to twenty-one of the latter, or twenty-three parts by weight of oxygen and seventy-seven of nitrogen; it generally contains also a variable proportion of the vapor of water, and a very small quantity of carbonic acid gas, being only about four volumes to 10,000 of air. Its constituent parts are easily separated, as it is a mechanical mixture and not a chemical compound, though the mixture by diffusion is so complete that chemists have not been able to ascertain any difference in the composition of air taken from all parts of the world, and from different heights, up to the highest point which has to this time been attained.

The atmosphere presses on the surface of the globe, and every being on it, with a force of about fifteen pounds to every square inch of surface, but as it presses equally in all directions, upwards as well as downwards, its weight cannot be perceived unless the pressure be removed from one surface by some artificial means.

Atmospheric air contains, besides the oxygen and nitrogen, its principal constituents, a small proportion of carbonic acid gas, as has been mentioned, and this may be shown by filling a tube about half full of lime-water, and shaking it with the air contained in the other half, when it will become slightly turbid from the insoluble carbonate of lime formed.

When we consider that every living animal is constantly consuming oxygen, and replacing it by carbonic acid gas, and that all burning bodies, fires in our dwellings, furnaces, artificial lights of all kinds, act in the same way in abstracting the oxygen from the air, and replacing it by immense quantities of carbonic acid gas, which is a poison to all animals who breathe, or attempt to breathe it, we must wonder what becomes of this irrespirable gas, as it is found to exist in the air in quantities so minute, and by what means the oxygen is restored, and the air again made fit for respiration. This is effected by one of those laws which the wisdom of the Creator has impressed upon matter, by which one part of creation as it were balances another, and all proceeds in an endless circle of change. This carbonic acid, which is so poisonous to animal life, is the food of the vegetable world, plants having the power of taking up the carbonic acid into their pores; converting the carbon into their own substance, and rejecting the oxygen, which is again respired by animals, &c. In the same way, all animal refuse is the food of vegetables, and is used under the name of manures.

The atmosphere contains also a variable quantity of vapor of water, invisible as long as it is in the state of vapor, but it may be rendered obvious by bringing any very cold body into warm air, when the vapor will condense on the cold body in the form of small drops of water. A tumbler of fresh-pumped water brought into a crowded room is almost immediately covered with moisture, and it may also be seen on bottles of wine which have been put into ice before coming to table. Fogs are occasioned by the condensation of vapor produced by mixing a current of warm air with a colder air. The banks of Newfoundland are notorious for dense fogs, occasioned by the warm air brought from the south by the great Gulf Stream, mixing with the cold air from the Arctic regions, and thus precipitating the vapor in a visible form, rendering everything but itself invisible. The famous London fogs depend upon the same precipitation of the vapor of water, with the addition of the smoke from the numerous sea-coal fires, which give it that interesting yellow tinge for which it is so remarkable.

Aqueous vapor appears to impart a transparency to air, and permits objects to be seen more distinctly in proportion to its quantity; hence, when distant hills appear nearer, and objects upon them more distinct than usual, rain may be expected, the air being fully charged with vapor ready to be deposited on the slightest cause.

Hydrogen.

Hydrogen gas is the lightest substance known, being fifteen times lighter than atmospheric air. It is colorless and transparent, incapable of supporting combustion or respiration, but is itself combustible. Hydrogen, as its name implies (being derived from two Greek words, signifying the generator of water), is a constituent of water in the proportion of one-ninth by weight, and is always obtained by decomposing that fluid, by presenting to it some body to take up its other ingredient, oxygen, and so set the hydrogen at liberty. If the steam of water be passed through a red-hot gun-barrel, containing iron filings, the water is decomposed, the iron taking the oxygen, and the hydrogen comes over in torrents; but as every one has not a gun-barrel and furnace to heat it, the usual mode is to employ dilute sulphuric acid, and iron filings, or zinc, in small pieces, and it may be collected over water by means of a bent tube issuing from the bottle in which it is formed. It is so light that it was used to fill balloons before coal gas was to be had, and if you procure a light air-tight bag of silk, or thin membrane, such as a turkey’s crop, and fill it with gas, it will ascend rapidly, and dance about the ceiling of a room.

Experiments.

1. Attach a tobacco-pipe to a bladder filled with this gas, and blow some soap-bubbles with it; they will rise very rapidly, and if a lighted taper be applied to them they burn.

If you mix in a soda-water bottle one-third of oxygen with two-thirds of hydrogen, and apply flame, the mixture will explode with a sharp report. Great care must be taken in all experiments with the mixed gases. To avoid danger the gases are placed in separate India-rubber bags, and are only brought together at the jet. This is an expensive apparatus, and should only be used by experienced persons.

2. If a jar of this gas be held with its mouth _downwards_, and a lighted taper passed up well into the jar, the taper will be extinguished, and the gas take fire, and burn quietly at the mouth of the jar; if mixed with oxygen or atmospheric air, it will explode.

Hold open the jet of hydrogen issuing from a small tube, hollow cylinders of glass or earthenware, Florence flasks, or hollow glass balls, and musical sounds will be produced, which were supposed to depend on some peculiar property of hydrogen gas, until Mr. Faraday tried flame from coal gas, olefiant gas, and even the vapor of ether, when the sounds were still produced, and he attributed them to a continuous explosion, or series of explosions, produced by the union of oxygen with the hydrogen of the flames.

Water.

With oxygen, hydrogen unites to form the important compound water, which exists not only in the obvious form of oceans, rivers, lakes, rains, dews, &c., &c., but is found intimately combined with many substances, giving them some of their peculiar properties. Many crystals have a definite proportion of water combined with them, and on losing this water they lose their crystalline form. Many acids also cannot exist as acids without water. The slaking of lime depends upon the union of water with the lime, the dry powder resulting from the process being a _hydrate_ of lime, the water having become _solidified_, and in passing from the fluid to the solid state gives out its latent caloric, producing the heat observed during the process. When a large quantity of lime, a barge-load for instance, has got wetted by accident, the heat evolved has been sufficient to set fire to the barge.

At the temperature of 32° of Fahrenheit’s thermometer, water loses its fluid form, and becomes ice. As it solidifies, it starts into beautiful crystals, which unite and cross each other at determinate angles. Ice is lighter than the water on which it floats, forming a protection to the water beneath, and preventing it from being frozen so rapidly; else, if the ice were _heavier_ than water, and consequently sank as soon as formed, each portion of water would be frozen in its turn, until rivers became solid throughout, and every living creature in them must be destroyed. Now, the temperature of the water under the ice is seldom much below 40°, and if care be taken to break holes at intervals to allow access to the air, the fish and other aquatic animals seldom suffer even in our coldest winters.

Although it is impossible to raise ice even one degree above 32° without thawing, it is not difficult to reduce water many degrees below that point without freezing it.

In order to obtain both the constituents of water in a separate state, it must be decomposed by galvanism, each pole of a battery terminating in a separate tube containing water, when the result will be that at the positive pole oxygen gas will be evolved, and hydrogen at the negative, the latter being double the quantity of the former. Now, if you mix the gases thus obtained, introduce them into a vessel called a “Eudiometer,” and pass an electric spark through them from a Leyden vial, a sudden flash will be seen, and the gases will entirely disappear, being again converted into water. If you have a mercurial trough, and perform this experiment over mercury, the inside of the eudiometer will exhibit minute drops of water. Thus you have proved both by _analysis_ and _synthesis_, that water consists of oxygen and hydrogen, in the proportion of one volume of the former to two of the latter.

Experiment.

Take some perfectly pure distilled water, filter it, surround it with a mixture of light snow, or powdered ice, and salt, taking care to keep it perfectly still, a thermometer having been previously placed in it. The mercury will gradually sink many degrees below the freezing point 32° (it has been reduced as low as 4°), the water still remaining fluid; when all at once, either from shaking the table, or simply because the reduction can be carried no further, it suddenly starts into ice, and the thermometer jumps up at once to 32°, where it remains until the whole is frozen, when the temperature gradually sinks to that of the surrounding medium.