40 Changes lohich take place in the Field 



a large surface is exposed to the air, and the alcohol transformed 

 into aldehyd by oxidation. Alcohol consists of 4 equivalents of 

 carbon, 6 of hydrogen, and 2 of oxygen, its composition conse- 

 quently may be expressed by the formula C^ Hg Og. By taking 

 up 2 equivalents of oxygen from the air alcohol becomes changed 

 into aldehyd with the production of 2 equivalents of water. 

 This simple change may be represented as follows : — ■ 



Ji^^^:}^ from^urAir. AMehycl^ Water. 



C, He O, + 2 = C, H, O2 + 2 H O 



Aldehyd thus differs from alcohol by containing 2 equivalents 

 less of hydrogen. The principal interest with which aldehyd is 

 invested arises from the facility with which it absorbs oxygen, 

 in consequence of which it readily is transformed into acetic 

 acid. The addition of 2 equivalents of oxygen to aldehyd is all 

 that is required for this change, as will be seen from the following 

 formula : — 



Aldeh}-d. 2 Oxygen. Acetic Acid. 



cTnTa + 20 = H o, c, h, d. 



This oxidation of aldehyd is accompanied with the evolution 

 of much heat. If the supply of air be insufficient,'the acidifica- 

 tion of dilute alcoholic liquids or substances capable of entering 

 into alcoholic fermentation may become so imperfect that the 

 alcohol is merely changed into aldehyd — a product intermediate 

 between alcohol and acetic acid ; and as aldehyd is an extremely 

 volatile substance, it may escape without becoming further 

 oxidised into acetic acid. In the interior of a closely packed 

 hay-rick in an active state of fermentation, in which the sugar 

 is first converted into alcohol and carbonic acid, the supply 

 of air is necessarily but limited, and hence it happened in the 

 case before us that although the vapours of aldehyd emanating 

 from the clover hay-rick were so overpowering as to render it 

 unsafe for a man to stand on the rick, yet so little acetic acid 

 was formed in the hay that I did not consider it worth while to 

 determine the amount quantitatively. 



jNIy observations on the changes which badly-made hay under- 

 goes in the stack show clearly that excessive fermentation destroys 

 sugar, one of the most valuable constituents of hay, which passing 

 first into alcoholic fermentation is finally lost, either in the shape 

 of aldehyd or that of acetic acid, according as the supply of 

 air is more or less copious. 



A glance at the following Table will show that the hay, as con- 

 taining 38 per cent, of water, was far too wet for stacking. 



