LESSONS IN CEEMiSTKY. 



235 



2173 = 



^l* 30 shillings VV shllliags = 4i(t hillings. 



M7w 



P ' X 1" 



HI shillings = -^ pence - f JJ pence 4,Vi pence. 

 {ft pence = . farthing* = 1JJ farthings. 



165) 112-000 (-678 

 MO 



1300 

 1155 



1450 

 1320 



130 

 Hence -2173 * 4s. 4d. and '678 farthings. 



EXERCISE 4.9. EXAMPLES IN REDUCTION OF DECIMALS. 

 Reduce 



1. 4s. 9d. to the decimal of 1. 



2. 10s. 9d. to the decimal of 1. 



3. 17s. 7d. to the decimal of 1. 



4. 6Jd. to the decimal of a shilling. 



5. 2 furlongs 2 rods to the decimal of a mile. 



6. 3 hours a minutes to the decimal of a day. 



7. 5 Ibs. 4 oz. to the decimal of a cwt. 



8. 15 rniuutes 30 seconds to the decimal of an hour. 



9. 7 ounces 8 drachms to the decimal of a pound. 



10. 1 guinea to the decimal of a moidore, and 2s. 6d. to that of 



1 guinea . Deduce from your results what decimal 2s. 6d. is 

 of a moidore. 



11. 2 roods 10 perches to the decimal of an acre. 



12. 18s lO.id to the decimal of a guinea. 



13. What decimal is a day of a year, and 3s. 7Jd. of 18s. 2Jd. ? 



14. What decimal is a pound of a cwt., and 2s. 9Jd. of 13s. lOid. ? 



15. Express I of 3 Ibs. 8 oz. as a decimal of 2 qrs. 15 Ibs. 7 oz. 



16. Reduce -43 of 2 17s. 6d. to the decimal of 5 15s. 

 Find the value of 



17. '725 in shillings, etc. 



18. -1325 iu shillings, etc. 



19. '825s. iu pence, etc. 



20. *435 Ibs. iu ounces and drachms. 



21. '275 miles in rode, yards, otc. 



22. -4258 days iu hours, etc. 



23. '845 hours iu minutes, otc. 



24. Reduce 4s. 75d. to the decimal of '01 of 1. 



25. Find "3 of a pound in shillings, pence, etc. 



26. Reduce 



* I" t T VV 



Find tho valuo of 



27. -890625 of 1 in shillings, pence, etc. 



28. -27 x -i of 2s. 9',d., and reduce the result to the decimal of & 



pound to 4 places. 



29. -23 of 2 + '345 of 8s. 6d. 1'35 of 5s. 



30. - -.- -- 53 O f a cu bic yard. 



235 -03 



of 1 to the decimal of a guinea. 



KEY TO EXERCISE 48, LESSON XXIX. (Vol. II., page 198). 

 N.B. Tho fractional parts of a farthing are neglected in these results. 



1. 

 2. 



3. 

 4. 

 5. 

 6. 



7. 



8. 







220 1 



1625 9 



212 4 



411 13 



2290 6 



135 12 



78742 2 



3456 16 





 865 



1358 



1810 

 144 



1895 

 163 



2226 



8. d. 



4 7; 



6} 



3 3} 



7 3| 

 o ii| 



9 



8 5} 



LESSONS IN CHEMISTRY. VIII. 



WATER (continued). PEROXIDE OP HYDROGEN. 

 THE purest water in nature ia rain-water. The sun evaporates 

 moisture, which ia condensed in the upper regions of the atmo- 

 sphere, and descends again as rain thus undergoing the process 

 of distillation. The only impurities rain-water can contain 

 are small quantities of the gases which compose the atmosphere 

 oxygen and nitrogen, and carbonic acid gas ; and in passing 



through tho air which overhangs towns, it dissolves sulphurous 

 acid gas and ammonia, but of these only the slightest trace. 



When rain-water percolates through the earth, it dissolve! 

 various Halts which it finds in its coarse. These are moat u*uaJly 

 calcium carbonate, CaCO, (chalk) ; common Halt, NaCl. (sodium 

 chloridu) ; calcium sulphate, CaSO 4 ; magnesium sulphate ftnd 

 carbonate, MgSO 4 and MgCO s . The water in the neighbourhood 

 of London contains about eighteen grains of chalk in each gallon. 



Mineral Waters are waters impregnated with a large propor- 

 tion of any one of these salts. Generally their temperature is 

 higher than the surface of the earth where they make their appear- 

 ance, and most usually they occur in volcanic neighbourhoods. 



Chalybeate springs contain iron, which they deposit on their 

 channel, making the water-course red with iron-rust. The 

 Cheltenham springs are of this kind, but they are of frequent 

 occurrence in the neighbourhood of iron beds. 



Seltzer water, and those of a kindred nature, owe their effer- 

 vescence to the escape of carbonic acid gas, of which they 

 contain large quantities. 



Harrogate water owes its offensive smell to the presence of 

 sulphuretted hydrogen gas. 



tialine springs, such as those at Epsom, abound in magnesium 

 sulphate. The Cheltenham springs also contain saline matter 

 sodium sulphate, Na,SO 4 and common salt. 



The presence of these salts may be readily detected by the 

 tests given under the various substances. 



Most of these waters are medicinal, but none of their contents 

 are pernicious. This is, however, not the case with organic 

 matter, which some " surface " waters contain. We shall take 

 London as an instance. The city is built on gravel, below 

 which is a bed of clay, known as the " London clay." The rain 

 percolates through this gravel, and is arrested by the clay ; a 

 well which is sunk down to the clay is soon filled with this water. 

 The liquid is bright, sparkling, very refreshing, and in about 

 the same proportion as its apparent good qualities recommend 

 it, so are its contents deleterious. Animal and vegetable matters 

 as they decompose give rise to the formation of nitrates, which 

 are readily soluble, and the water becomes impregnated with 

 these salts, and it also holds some of the animal matter in solu- 

 tion. These impurities are classed under the name of " organic 

 matter." To the use of such water the origin of the malignant 

 epidemics which sometimes scourge our towns is frequently 

 traced. Water containing organic matter, when evaporated to 

 dryness, leaves a brown residuum, which chars when sufficiently 

 heated. It may, also, be tested for by permanganate of potash. 

 If a dilute solution of this salt be added to distilled water which 

 has been acidulated with a few drops of sulphuric acid, and 

 then raised to CO Cent, for half an hour, it will be found to re- 

 tain its pink colour ; but if water containing organic matter be 

 used, the solution is rendered colourless in a few minutes. The 

 water with which the companies supply London is got from the 

 chalk which lies beneath the clay. 



The reader must have frequently noticed that it is a disagree- 

 able and indeed difficult matter to wash in some waters. These 

 are termed " hard waters." Their peculiarity arises from the 

 fact that they contain salts whose bases are lime and magnesia. 

 When soap is dissolved in them, these mineral salts and the 

 soap act upon each other, or, in chemical language, undergo 

 a double decomposition, the result of which is the formation 

 of insoluble compounds of the fatty acids of the soap (oleic 

 and stearic) and the bases of the salts. These oleatea and 

 stearates of lime and magnesia, being insoluble, are, of course, 

 precipitated, but they are of a stringy nature, and adhere to 

 any kind of textile fabric, rendering it difficult to wash clothes 

 in such waters. 



Various ways have been proposed to " soften " water, the 

 object of which will be at once comprehended when we state 

 that those salts are not by nature soluble in water, but are ren- 

 dered so by the presence of carbonic acid gas. If, for instance, 

 some powdered chalk be shaken up in a bottle of water, the 

 liquid will become milky, but if the experiment be repeated with 

 a bottle of " soda-water " freshly opened, the chalk will dissolve, 

 and the water retain its transparency. If by any means the 

 carbonic acid gas can be driven out of the hard water, its salt* 

 will be precipitated, and it will become soft. This may partially 

 , be effected by boiling ; hence the explanation of the calcareous 

 deposit found at the bottom of boilers. This fact may be readily 

 exhibited by boiling a flask of bard water-, after some minutes it 



