68 



Exjjlanation of Terms. 



Vol. 11. 



straw, he will not find corn and oil cake pro- 

 fitable, unless beef promises to be very high, 

 and corn and cake very cheap. Whatever 

 the food, it cannot be too often repeated, that 

 small quantities are to be given at a time; 

 that troughs, cribs, &c. are to be kept very 

 clean, and that litter must be so plentiful, 

 tliat the beasts have clean hides and warm 

 beds. Straw given to stock, should be con- 

 stantly made use of as soon after threshing 

 as possible; for if exposed to the influence of 

 the atmosphere, it becomes either musty or 

 too dry ; and in that state cattle neither relish 

 nor thrive on it so well. It is time to take a 

 critical and inquisitive view of your barn, 

 cellar, and all other buildings where injury 

 can be sustained by the agency of frost, and 

 wherever it is possible, close every avenue 

 to the intrusions of that unwelcome visitant. 

 There is no danger of using too much salt in 

 preserving fat pork. 



Ssftla-iiatioii of Terms. 



Concluded. 



47. Acids — are substances of a sour taste. 



The acids are very numerous. Their most 

 distinguishing properties are, 1st, that they 

 change to rec? those colors of vegetables which 

 the alkalies change io green ; 2lI, They com- 

 bine with alkalies, and thereby form various 

 kinds of salts. 



Thus, the combination of muriatic acid with 

 soda forms common salt. 



Some of tlie acids are met with in a solid 

 state; others in a fluid state, as vinegar ; and 

 others in a gaseous state. Of the latter is Car- 

 bonic Acid, which requires a more particular de- 

 scription. 



The carbonic acid, when uncombined with 

 any other substance, is always met with in a 

 state of gas, and hence it is called Carbonic 

 Acid Gas- It is the same substance which was 

 formerly czXleA fixed air. It exists in a small 

 proportion in the atmosphere. It destroys life 

 and extinguishes the light of a candle when im- 

 mersed in it. It is disengaged largely from 

 liquors, such as beer, cider, or wine, when in 

 the act of fermentation. It is this gas which 

 produces the many unhappy accidents in some 

 subterraneous caverns, inclosed cellars contain- 

 ing large quantities of fermenting liquors, in 

 some deep wells, and in bed chambers, warmed 

 by burning charcoal in pans. 



This acid combines with a great variety of 

 substances, which are then called carbonates. 

 It exists in marble, chalk and limestone in differ- 

 ent proportions, all which are called carbonates 

 of lime, and the burning of limestone is for 

 no other purpose, but to expel the carbonic acid, 

 which is done by heat, in which operation the 

 limestone loses nearly half its weight. 



The alkalies attract it from the atmosphere. 

 It is present in pot and pearl ashes, from which 



it is disengaged by the addition of a stronger 

 acid, as every one may have seen in throwing 

 pearl ash into cider, as some people do to drink 

 in the morning. The acid in the cider in unit- 

 ing with the pearl ash, displaces the carbonic 

 acid, which rises in the form of gas through the 

 liquor, producing much foam with a hissing 

 noise, caWeA Effervescence. 



48. Atmospheric Air — or the air which 

 surrounds this earth, is a mixture of two dif- 

 ferent kinds of air, called Oxygen vlwA Azote. 

 It likewise contains a small proportion of 

 Carbonic Acid Gas, a substance already de- 

 scribed. 



It is well known that no animal will live, or 

 fire burn, without air ; but it is that part of the 

 air called oxygen which is necesary for both. 

 It is this which supports life and combustion ; 

 and where there is no oxygen, an animal will 

 die and a light will be extinguished as suddenly 

 as where there is no air at all. 



Ail this may be made plain by a very easy 

 experiment. Take a lighted candle, put it into 

 a candlestick, and set it into a pail of water so 

 deep as that the light of the candle may rise 

 three or four inches above the surface of the wa- 

 ter. Then take a deep tumbler, or a wide 

 mouthed decanter, invert it, and let it down 

 over the candle till the brim shall dip into the 

 water. As the candle continues burning, the 

 water will be seen rising in the decanter till it 

 shall be about one quarter part full, when the 

 candle will suddenly go out. Now the reason 

 of the water's rising in the decanter, is, because 

 the oxygen is gradually consuming by the 

 lighted candle ; and the reason that the candle 

 goes out is, that the oxygen at that instant is all 

 gone, or has all been expended in the combus- 

 tion. What is then left in the decanter will be 

 the other part or kind of air called azote, and if 

 a small animal should be introduced into this 

 air it would die as suddenly as if it had no air at 

 all. 



Oxygen gas (for you must remember that 

 every substance in the form of air is called a gas) 

 is a very wonderful substance. It unites with 

 iron, when exposed to the atmosphere, for any 

 length of time and converts it into rust ; it 

 unites with melted pewter or lead and converts 

 them into dross, or oxyde, as it is called ; it 

 unites with another kind of gas, called llydro- 

 en, and forms water. Yes, what perhaps it 

 may surprise you to know, ivater is not a sim- 

 ple, as most people suppose, but a compound 

 substance, composed of Oxygen and Hydrogen 

 gas. Both its decomposition and its composi- 

 tion are common experiments in every chemical 

 room. 



Oxygen likewise is one of the ingredients in 

 the composition of acids, all which are compound 

 substances ; hence oxygen has been called the 

 great acidifying principle. Thus, it unites with 

 sulphur, in the act of combustion, and forms 

 sulphuric acid, or oil of vitriol as it was former- 

 ly called ; it unites also with carbon or char- 



