CHAPTER XIX.

CARBONIC ACID GAS.

Q. _What is CHOKE DAMP?_

A. _Carbonic acid gas_ accumulated at the bottom of wells and pits, which renders them noxious, and often fatal.

Q. _Why is not this carbonic acid TAKEN UP by the AIR, and DIFFUSED, as it is in cities?_

A. Because (being _heavier than common air_) it cannot _rise from the well or pit_; and no wind can get to it to blow it away.

Q. _Is CARBONIC ACID WHOLESOME?_

A. No; it is _fatal to animal life_, when inhaled through the mouth; acting on the stomach, _as a narcotic poison_ (i. e. a poison which produces death from drowsiness).

Q. _How can any one KNOW, if a place be infested with CARBONIC ACID GAS?_

A. If a pit or well contain carbonic acid, _a candle_ (let down into it) _will be instantly extinguished_. The rule, therefore, is this--Where a _candle will burn, a man can live_; but _what will extinguish a candle_, will _also destroy life_.

Q. _Why does a MINER lower a CANDLE into a mine, before he descends?_

A. Because the _candle will be extinguished_, if the mine contains carbonic acid gas: but if the candle is _not extinguished_, the mine is _safe_, and the man may fearlessly descend.

Q. _Why are PERSONS sometimes KILLED, by leaning over BEER VATS?_

A. Vats (where beer has been made) contain a _large quantity of carbonic acid gas_, produced by the "vinous fermentation" of the beer; and when a man incautiously _leans over a beer vat_, and inhales the carbonic acid, he is immediately _killed_ thereby.

Q. _Why are PERSONS often KILLED, who enter BEER VATS to clean them?_

A. Carbonic acid (being _heavier than atmospheric air_) often rests upon the _bottom of a vat_: when, therefore, a person enters the vat, and _stoops to clean the bottom_, he inhales the pernicious gas, which _kills_ him.

Q. _Why are the JUNGLES of Jarva and Hindostan so FATAL to life?_

A. Because vast quantities of _carbonic acid_ are thrown off by decaying _vegetables_; and (as the wind cannot penetrate the thick brushwood to blow it away) _it settles there_, and destroys animal life.

Q. _Why are PERSONS sometimes KILLED by having a CHARCOAL FIRE in their bed-rooms?_

A. When charcoal is burned, the _carbon of the charcoal_ unites with the _oxygen of the air_, and forms _carbonic acid gas_, which is a narcotic poison.

Q. _Why does the carbonic acid gas of a CHARCOAL FIRE RISE and DISPERSE itself about the room; whereas the carbonic acid gas of a BEER VAT SETTLES near the FLOOR?_

A. The carbonic acid gas of a charcoal fire _is heated_ by the _combustion of the fuel_, and rises; but the carbonic acid gas of a beer vat is _not_ heated, and, therefore, rests on the _bottom of the vat_.

Q. _Why do persons throw LIME into BINS to PREVENT their offensive SMELL, in summer time?_

A. Bins contain large quantities of _carbonic acid gas_, which readily _combines with lime_, and produces "_carbonate of lime_," which is entirely free from all offensive odour.

Q. _Why do persons throw LIME into SEWERS in summer time?_

A. Sewers (like bins) contain large quantities of _carbonic acid_, which readily _combines with lime_, and produces _carbonate of lime_; and thus the offensive gas of the sewer is neutralized.

Q. _Can carbonic acid be removed in any way BESIDES by LIME?_

A. Yes; _water_ thrown into a pit will disperse the carbonic acid.

Q. _What effect has WATER on CARBONIC ACID GAS?_

A. Water (under _pressure_) _absorbs_ carbonic acid gas; and _parts_ with it (when the _pressure is removed_) in the form of EFFERVESCENCE.

Q. _Why does AERATED WATER effervesce, when the CORK is removed?_

A. While the _cork was fastened down_, the water _absorbed_ the carbonic acid; but the moment _the pressure is removed_ (by taking out the cork) the gas is given out with _effervescence_.

Q. _Why does SODA WATER effervesce?_

A. Soda water contains 8 times its own bulk of carbonic acid gas, which makes its escape in _effervescence_, the moment that the _cork is removed_.

Q. _Why does GINGER POP fly about in froth, when the string of the cork is cut?_

A. All vinous fermentation produces carbonic acid gas. While the _cork is fast_, the water of the liquor _absorbs_ the carbonic acid; but the moment that the _pressure is removed_, the gas is given off in _effervescence_.

Q. _Why does BOTTLED ALE froth, more than DRAUGHT ale?_

A. Because the _pressure_ is greater in a _bottle_ than in a tub which is perpetually tapped: and effervescence is always produced _in proportion to the pressure_.

Q. _Why does bottled ALE and PORTER become "LIVELY" and FROTHY by being SET before the FIRE?_

A. The heat of the fire _expands the air_ (between the liquid and the cork), and as this air expands, _it presses the liquid down_, which causes effervescence.

Q. _What produces the FROTH of BOTTLED PORTER?_

A. The _carbonic acid gas_, produced by its _vinous fermentation_; which is _absorbed by the liquor_ so long as the bottle is _well corked_, but is _given off in froth_ as soon as the pressure of the cork is _removed_.

Q. _What gives the pleasant ACID taste to soda water, ginger beer, champagne, and cider?_

A. The presence of _carbonic acid_, generated by fermentation, and liberated by effervescence when the pressure of the cork is removed.

Q. _Why does fresh SPRING WATER SPARKLE, when poured from one vessel to another?_

A. Because fresh spring and pump water contain _carbonic acid_; and it is the presence of this gas _which makes the water sparkle_.

Q. _What is the FERMENTATION of BEER and WINE?_

A. The production of carbonic acid gas and al'cohol.

Q. _How is CARBONIC ACID GAS produced by FERMENTATION?_

A. Malt and fruit _both contain sugar_; and sugar consists of carbon, oxygen, and hydrogen. In fermentation, a part of the _carbon and oxygen_ of the sugar escape, _in the form of carbonic acid gas_.

Carbonic acid gas is a compound of carbon and oxygen, in the following proportions:--3 lbs. of carbon and 8 lbs. of oxygen will form 11 lbs. of carbonic acid gas. Now, 100 lbs. of white sugar contains 43 lbs. of carbon; 50 lbs. of oxygen; and 7 lbs. of hydrogen.

Q. _How is AL'COHOL produced by FERMENTATION?_

A. The _hydrogen of the sugar_ combines with the _residue of the oxygen and carbon_ to form "AL'COHOL."

Q. _What is AL'COHOL?_

A. Al'cohol is the _spirit_ of wine or beer, obtained by _fermentation_.

(100 gallons of alcohol consist of 38 gallons of oxygen; 43-1/2 of carbon; 15 of hydrogen; and 3-1/2 of nitrogen.)

Q. _Why is BARLEY MALTED?_

A. Because _germination_ is produced by the artificial heat; and in germination the _starch of the grain_ is converted into _sugar_.

Q. _How is barley malted?_

A. The barley is _moistened with water_, and _heaped up_; by which means, great _heat_ is produced, which makes the _barley sprout_.

Q. _Why is not the BARLEY suffered to GROW, as well as SPROUT?_

A. Plants in the _germ_ contain _more sugar_ than in any _other state_; as soon as the germ _puts forth shoots_, the _sugar_ of the plant is _consumed_, to _support the shoot_.

Q. _How is BARLEY PREVENTED from SHOOTING, in the process of MALTING?_

A. The barley is _put into a kiln_ as soon as it sprouts; and the _heat_ of the kiln checks or _destroys the young shoot_.

Q. _Why is YEAST put into BEER to make it WORK?_

A. Yeast supplies the beer with _nitrogen_, which is one of the ingredients of alcohol.

Alcohol consists of _oxygen_, _carbon_, and _hydrogen_, (obtained from the sugar of malt), and _nitrogen_, (obtained from yeast).

Q. _Why is it NOT needful to put YEAST into WINE?_

A. Because fruit contains _carbon_, _hydrogen_, _oxygen_, and _nitrogen_, in the form of "gluten;" and, therefore, ferments _spontaneously_.

(Gluten is explained fully in the Appendix.--Turn to the word in the Index.)

Q. _Does not MALT contain carbon, hydrogen, oxygen, and nitrogen, as well as FRUIT?_

A. No; the sugar of malt contains _carbon_, _hydrogen_, and _oxygen_, but _no nitrogen_; in consequence of which, _yeast_ (which contains _nitrogen_) is _added to the wort_.

Q. _Why do NOT GRAPES ferment while they hang on the VINE?_

A. 1st--Because the skin lets out the _water of the pulp_, which causes the grapes to shrivel and dry up: and

2ndly--The skin _prevents_ the admission of _oxygen into the pulp_, from the air without.

Q. _What is the FROTH or SCUM of fermented LIQUORS?_

A. _Carbonic acid gas_, which (being heavier than common air) _settles on the top of the liquor_, in the form of scum.

Q. _Why does a small piece of raw MEAT, or a few RAISINS improve FLAT BEER?_

A. 1st--Because they supply it with _nitrogen_ to form it into al'cohol.

2ndly--As the raw meat, &c. _putrifies_, it gives off _carbonic acid gas_ into the beer, which gives it "life."

Q. _Why is BEER FLAT, if the cask be open too long?_

A. Because _too much of the carbonic acid gas_ (produced by fermentation) is suffered to _escape_.

Q. _How is the CARBONIC ACID GAS of BEER generated?_

A. The saccharine (or sugar) of the malt is converted by _fermentation_ into carbonic acid gas and alcohol.

Q. _Why does BEER turn FLAT, if the VENT PEG be left OUT of the tub?_

A. Because the _carbonic acid gas escapes_ through the vent hole.

Q. _Why will NOT beer RUN OUT of the tub, till the VENT PEG is taken out?_

A. When the tap is turned, _air rushes through the tap_ into the bottom of the tub, and _holds the liquor in_.

The _upward_ pressure of air is illustrated by the

following simple experiment:--Fill a wine-glass with water; cover the top of the glass with a piece of writing paper; turn the glass topsy turvy, and the water will not run out. The paper is used merely to give the air a medium sufficiently dense to act against.

Q. _Why does the BEER RUN FREELY, immediately the VENT PEG is taken out?_

A. As soon as the vent peg is taken out, air rushes _through the vent hole_ at the _top of the tub_,--presses the liquor _down_, and _forces it through the tap_.

Q. _Why does liquor flow reluctantly out of a BOTTLE held upside down?_

A. Because the _upward pressure of the air_ prevents the liquor from flowing out.

Q. _Why should a bottle be held OBLIQUELY, in order to be emptied of its liquor?_

A. Because _air_ will then _flow into the bottle_, and help the liquor out by _balancing the upward pressure_.

Q. _Why does wine (poured from a bottle QUICKLY) SPIRT about without going into the decanter?_

A. The liquor fills the _top of the decanter_ (like a _cork_), and leaves _no room_ for the air inside _to escape_; therefore, the decanter (being _full of air_) refuses to admit the _wine_.

Q. _Why is BEER made STALE, by being exposed to the AIR?_

A. Because air _absorbs its carbonic acid_, which gave it "life."

Q. _Why is PORTER made STALE, by being exposed to the AIR?_

A. Because air _absorbs its carbonic acid_, which gave it "life."

Q. _Why does the EFFERVESCENCE of soda water and ginger beer so soon go off?_

A. Because air _absorbs the carbonic acid_, which produced the effervescence.

Q. _Why is BOILED WATER FLAT and insipid?_

A. Because the whole of the _carbonic acid is expelled_ by boiling, and _absorbed by the air_.

Q. _Why does WATER become FLAT and insipid, after it has been DRAWN some time?_

A. Because air _absorbs its carbonic acid_; and when its carbonic acid is absorbed, the water is flat and insipid.

Q. _Why should spring WATER (used for WASHING) be exposed to the AIR?_

A. Spring water _contains carbonic acid_; but (by being exposed to the _air_) this carbonic acid is _absorbed_, and the water becomes _more soft_.

Q. _Why does YEAST make BREAD LIGHT?_

A. Flour contains a small portion of _saccharine matter_ (or sugar); and the yeast (mixing with this) produces _fermentation_, as it does in brewing.

Q. _How does FERMENTATION make the DOUGH RISE?_

A. During fermentation, _carbonic acid gas is evolved_; but the sticky texture of the dough will not allow it to _escape_, so it _forces up little bladders_ all over the dough.

Q. _Why is DOUGH placed BEFORE the FIRE?_

A. 1st--Because the heat of the fire _increases the fermentation_: and

2ndly--It _expands the gas_ which is confined in the little bladders; in consequence of which, the bladders are _blown up larger_, and the dough becomes lighter and more porous.

Q. _Why is BREAD HEAVY, if the dough be removed from the fire?_

A. Because the dough _gets cold_, and then the air in the bladders _condenses_,--the paste falls,--and the bread is close and heavy.

Q. _Whence does the HEAT of FIRE arise?_

A. The _carbon of fuel_ (when heated) _combines with the oxygen of the air_, and produces _carbonic acid gas_: again, the _hydrogen of the fuel_ combining with _other portions of oxygen_, condenses into _water_; by which chemical actions _heat is evolved_.

Q. _Whence does the HEAT of our own BODY arise?_

A. The _carbon of the blood_ combines with the _oxygen of the air inhaled_, and produces _carbonic acid gas_; which produces heat in a way similar to burning fuel.

Q. _Whence does the HEAT of a DUNGHILL arise?_

A. The _straw, &c. of the dunghill_ undergoes _fermentation_ as it decays: the fermentation produces _carbonic acid gas_, and heat is evolved by a species of combustion (as in the two former cases).

Q. _What changes do VEGETABLES undergo from PUTREFACTION?_

A. The _hydrogen of the vegetables_ combines with the _oxygen of the air_, and forms _water_: again, the _carbon of the vegetables_ combines with _oxygen of the air_, and forms _carbonic acid gas_. Putrefaction, therefore, is only another species of combustion.

Q. _What changes do ANIMAL bodies undergo from PUTREFACTION?_

A. The same as vegetables, with this addition--they give out _ammonia_, _sulphur_, and _phosphorus_ also; which causes the _offensive smell_ of putrefying animal bodies.

Q. _Why is LIME heated by a KILN?_

A. All marl and chalk abound _in carbonic acid_; and (when heated by a fire) the carbonic acid _flies off in gas_, producing great heat.

Q. _What is MORTAR?_

A. Lime mixed with sand and water.

Q. _What is LIME?_

A. _Lime-stone burnt_ produces lime.

Q. _Why is the lime-stone BURNT, in order to make it into LIME?_

A. The fire _expels the carbonic acid_, and converts the hard lime-stone into a _loose powder_.

Q. _Why does MORTAR become HARD, after a few days?_

A. Because the lime _re-imbibes_ the carbonic acid of the air, which was _expelled by fire_; and the loose _powder_ again becomes as hard as the original _lime-stone_.

Q. _Why is MORTAR adhesive?_

A. When the carbonic acid is expelled, the hard lime-stone is _converted into a loose powder_, which (being mixed with sand and water) becomes a _soft and sticky plaster_; but, as soon as it is placed between bricks, it _imbibes carbonic acid again_, and hardens into _lime-stone_.