FOOD MANUFACTURE 35 



presence of light. The word " photograph" shows the same 

 use of the word light, and the process of " photography " 

 shows the same activity of light in causing chemical changes. 

 The first step in the process seems to be the " breaking up " 

 of the water and carbon dioxide into their constituent ele- 

 ments. Those who have studied chemistry know that water 

 is a combination of the two elements hydrogen and oxygen, 

 both of them gases, in the proportion of two parts of hydrogen 

 to one part of oxygen, so that the formula for water is H 2 O. 

 Carbon dioxide is also a combination of two elements, carbon 

 and oxygen, and its formula is C0 2 . To break up these two 

 substances, so that the water splits into the two gases that 

 compose it and the carbon dioxide splits into the gas and the 

 solid that compose it, is a process that requires a great dis- 

 play of energy, in the form of heat, electricity, etc., when 

 done in the laboratory ; but it is accomplished by the green 

 plant without any unusual display of energy. 



Following the breaking up (analysis) of the raw materials, 

 the elements are put together in new combinations, the 

 " putting together " being the " synthesis " referred to in 

 the -name photosynthesis. It must not be supposed that a 

 carbohydrate is the result of the first synthesis, for it is 

 reached only after a series of chemical changes. 



27. The product. The final product of photosynthesis 

 is reached when a carbohydrate is formed. If the raw ma- 

 terials and the final product are compared, certain important 

 facts become evident. The simplest method of comparison 

 is to use the following equation : C02 + H 2 = QHaO + O 2 . 

 The first side of the equation represents the raw materials, 

 and the other side represents the carbohydrate product and 

 the oxygen left over. CH 2 is not the formula for a car- 

 bohydrate, but it may be called the carbohydrate unit, which 

 by using various multiples becomes the formula of various 

 carbohydrates. For example, a simple carbohydrate is 

 C 6 Hi 2 O 6 , in which 6 is the multiple, and most other carbo- 



