1846. 



GENESEE FARMER. 



27; 



fire. It burns with a feeble, and almost invisi- 

 ble light in the day time. 



How do you know that the gas given off comes 

 from water ? 



17. Because neither the sulphuric acid, m r iron 

 contains a particle of hydrogen ; and water does. 



What becomes of the oxygen in the decom- 

 posed water ? 



18. It unites chemically with the iron filings 

 and forms a compound called oxide of iron. — 

 With this oxide the acid combines chemically 

 and forms the salt called copperas, or sulphate of 

 iron. When the hydrogen gas that escapes from 

 the bottle in the manner described, is burnt, what 

 new compound is formed with this inflammable 

 gas? 



19. No other compound is formed than that of 

 ivater. 



How will you demonstrate the fact that, water 

 is formed when hydrogen is burnt in the air ? 



20. By placing a glass tube an inch in diame- 

 ter and 30 inches long over the burning gas, va- 

 por will be condensed on the inside of the tube, 

 although quite dry at the beginning of the exper- 

 iment. The term hydrogen is derived from 

 Greek wojds that signify, "I form water." Wa- 

 ter can not be formed without hydrogen. 



What are a few of the distinguishing charac- 

 teristics of hydrogen ? 



21. It is the lightest body in the world that 

 can be weighed ; being 1-5 times lighter than 

 common air, and 16 times lighter than oxygen. 

 It was formally used to inflate balloons. It is in- 

 visible and devoid of taste and smell. 



If oxygen is 16 times heavier than hydrogen, 

 and 8 parts by weight of the former unite with 

 1 of the latter to form water, must not two vol- 

 umes of hydrogen combine with one of oxygen 

 to give the relative weight of these elements, as 

 8 to 1 ? 



Certainly. Let 1 cubic inch represent 1 of 

 hydrogen, thus — 



and half a cubic inch will represent 8 of oxygen. 

 The two make one of water, whose equivalent 

 number is 9. 



Do all chemical compounds have Si fixed equiv- 

 alent number ? 



23. They do ; as will be abundantly shown in 

 the course of our Study. 



Do the gases oxygen and hydrogen ever com- 

 bine without forming liquid water ? 



24. They do ; and instead of forming water they 

 make gaseous steam. 



In that case is there any condensation of the 

 volumes of the oxygen and hydrogen at their 

 chemical union 1 



2.5. There is. The condensation is just equal 

 to one t'liird of the bulk of the two gases, i. e. the 

 whole volume of the oxygen is merged into that 

 of the hydrogen. ■ 



When a cubic foot of water is expanded into 

 steam, how many cubic feet will the latter fill 1 



26. 1696. 



V\ hen a quart of water is made into steam, at 

 the temperature of boiling heat (212°) and the 

 steam condensed in water at 62°, how many 

 quarts will it heat up to the boiling point ? 



27. About 6 J quarts. 



How will you explain this phenomenon, see« 

 ing that the steam when tested by a thermometer 

 is no hotter than boiling water ? 



28. If we place over a steady fire — that of a 

 spirit lamp is best — water in a thin glass basin, 

 its temperature will gradually riee till it reaches 

 212° when it boils, and the water becomes no 

 hotter, but ebulition continues so long as any 

 water remains. Let us suppose that tlie temper- 

 ature of the water was 62-' when placed over the 

 fire ; and it took a steady heat 6 minutes to boil 

 it. The gain in temperature in 6 minutes wag 

 the difference between 62° and 2] 2°, or 1.50.— 

 This divided by 6, and it is seen that the gain 

 was equal to 2.5^ a minute, for 6 times 25=150. 

 With the same uniform heat from the lamp, it 

 will take 40 minutes to evaporate all tlie water. 

 40 multiplied by 25° (the amount of heat impar- 

 ted to the water in each minute,) give 1000° of 

 heat as the sum total acquired by the steam. To 

 raise the temperature of a quart of water at 62'^ 

 up to 212°, will take 150° of heat. But it has 

 been demonstrated that, although steam shows by 

 the thermometer only 212° of heat, it has re- 

 ceived 1000°, and when condensed, will raise as 

 many quarts from 62° to 212 as the difference 

 (150) is contained in 1000 ; which is 63 times. 



In what condition do these 1000° of heat exist 

 in steam, that a thermometer shows no more 

 than 212° ? 



29. In the condition of latent or hidden heat. 

 I have stated the fact that, water in being change4 

 into steam, expands to 1696 times its former vol- 

 ume. It is an important natural law that, the 

 capacity of a body to hold insensible heat is in- 

 creased as it passes from a denser to a rarer or 

 thiner medium. Steam is a vastly rarer medium 

 than water ; and in making the transition, it ren- 

 ders a large amount of sensible heat insensible, 

 or latent. All this is made sensible again, when 

 steam, or any other body is condensed. 



Water is a rarer medium than ice. Will you 



pretend to say that water at 32° in freezing into 



ice at the same temperature, gives out sensible 



heat ? 



30. Certainlyldo. It givesoutnolessthan 140". 



How can you prove that ? 



31. Dissolve a pound of ice at 32° in a pound 

 of water at 172°, and you will have 2 lbs. of wa. 

 ter at 32° instead of 102°, the mean of 32° and 

 172°. This simple experiment demonstrates that 

 ice in liquifying absorbs 140-^ of heat and hides 

 it, which of course it will give out on freezing. 



Is there any other similar iiistance where the 



