APPENDIX 

 PHOTOSYNTHESIS 



The chemistry of photosynthesis is not completely known, 

 but some of the simpler aspects of it may prove valuable to 

 the student. The chemist's formula for water is H 2 O, in 

 which II stands for hydrogen and O for oxygen, and the 

 figure 2 indicates that two parts of hydrogen are united with 

 one part of oxygen. Similarly, CO 2 indicates that one part 

 of carbon is united with two parts of oxygen to form carbon 

 dioxide. When these compounds are broken up, there is, for 

 a very brief time at least, free C, H, and O. If one unit of 

 each compound (H.,O and CO.,) is thus broken up, there 

 will be two.H, one O, one C, and two O or in all three O. 

 After photosynthesis has been going on for some time, starch 

 is usually formed. Starch consists of (C 6 H 1Q O 6 ) n . This 

 means that six parts of carbon, ten parts of hydrogen, and five 

 parts of oxygen unite to form starch, and the n means that 

 the unit C tt II 10 () 6 does not appear singly, but that an unknown 

 number of them are united. Disregarding the fact that several 

 of the starch units are held together, and considering the single 

 unit C 6 II 10 O 6 , we may be able to see what happens in the work 

 of photosynthesis. To secure the amount of carbon necessary 

 to form starch, six times the unit CO 2 must be taken, since 

 six units of carbon are to be used. To secure the needed 

 amount of hydrogen, five times the unit HO must be used, 

 since there must be ten units of hydrogen, and two are secured 

 with each unit of water. We have therefore 6 (CO 2 ) and 

 5(H 2 O). When the energy of the sun has broken these 

 things into their constituent parts, there are 6 (C), 12(O), 

 10 (H), and 5 (O) or 17 (O) in all. But starch consists of 

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