116 Traksactions of the American Ixstjtute. 



leaving phosphates of lime and soda in the bread. There remained 

 one thing more. The phosphoric acid in the normal wlieat is largely 

 combined with potassa. Of the ash which burned wheat leaves, 

 nearly iifty per cent is phosphoric acid, and about thirty per cent is 

 potassa, with small amounts, relatively, of lime, magnesia, so<la, silica, 

 and iron. That my self-leavening flour might contain phosphate of 

 potassa, I prepared my phosphoric acid, in combination with potassa 

 and lime, or taking the acid phosphate of lime I added chloride of 

 potassum to the self-leavening flour, which, besides furnishing phos- 

 phate of potassa on the addition of water, set free liydrochloric acid. 

 The hydrochloric acid being more soluble, acted more promptly on 

 the bicarbonate of soda, producing chloride of sodium (common salt), 

 and setting free the carbonic acid to inflate the dough. Thus consti- 

 tuted, the self-raising flour has, in most respects, very nearly the 

 nutritive value of. the normal wheat, without the inferior color, and 

 the liability to rapidly sour of the whole wheaten meal. You will 

 pardon me, I am sure, if I read to you an extract from a letter of 

 Baron Liebig, to whom the world is more indebted than to any living 

 scientific man, and who has given great attention to this subject. 

 He wrote me some time since as follows: ''^ I consider this one of the 

 most iiseful gifts which science has made to inankind. It is certain 

 that the nid)'itive value of flour vnll l)e increased, ten per cent hy your 

 phosphatic hread preparation^ and the result is precisely the same as 

 if the fertility of our wheat fields had been increased hy that amount. 

 What a wonderful result is this .^" 



Obsctjke Phenomena of Beead. 

 "Wliile my bread continues to bake, let me direct your attention to 

 two or three points, which have been regarded as obscure, but which 

 it has been my fortune in some degree to clear up. What are the 

 changes that attend the conversion of flour into bread ? We liave 

 already seen that the flour is composed of gluten and starch, and 

 glanced at the changes produced by fermentation. When starch is 

 examined with the microscope, it is found to consist of little sacs, 

 sometimes groups of them aggregated together, which sacs are com- 

 posed of homogeneous membrane, suggesting collodion in appearance, 

 w-ithin which the granules of starch proper are deposited. If you 

 subject these starch sacs to heat, they burst open, and then if the 

 starch granules come in contact with water, they liquify to form fluid 

 starch, a sort of mucilage. These diagrams will illustrate what I have 

 said. (Diagram F.) If, in this condition of mucilage, the starch be 



