POTASSIUM PHOSPHATE IN CELLS. 19 



required. It may further be mentioned in this connection that, accord- 

 ing- to Miintz, the amount of free fatty acids increases during germina- 

 tion, which is to be expected when lecithin is formed from fat. From 

 all the observations cited it will be seen that lecithin plays an impor- 

 tant role; and as its formation is made possible only when phosphoric 

 acid is present, one of the functions of this acid at once becomes 

 intelligible. 



PHOSPHORIC ACID IN CHLOROPHYLL. 



As Trecul, Gautier, and Hoppe have shown, the crystallized chloro- 

 phyllan also contains phosphoric acid (1.39 per cent); indeed, for the 

 formation of the chlorophyll green the presence of phosphoric acid is 

 absolutely required (seep. 21). The opinion has been expressed that 

 the crystallized chlorophyllan is a kind of lecithin. Others, however, 

 have declared it a mixture. 



POTASSIUM PHOSPHATE AS A CELL CONSTITUENT. 



That the secondary potassium phosphate as such has also an impor- 

 tant physiological function becomes probable from its general occur- 

 rence in the living organisms. Relatively large proportions of it are 

 found in j^east cells, in seeds, in the liver and muscles, and, in fact, in 

 all cases where special demands for great chemical achievements are 

 made. It causes the weak alkaline reaction of protoplasm and is 

 probably present in loose combination with certain proteins, from 

 which even treatment with water will often easily remove most of it. 

 A further special function of phosphoric acid is the use of calcium 

 phosphate for the formation of bones. The blood ash of cattle con' 

 tains 1 to 6 per cent and of man 9 to 11 per cent of phosphoric acid. 



The dry substance of muscles contains about 1 per cent of mineral 

 matter, of which again nearly two-thirds consist of dipotassium phos- 

 phate. This is also nearly the proportion found in beer yeast. Wheat 

 grains contain from 1 to 2 per cent ash, of which nearly one-half con- 

 sists of potassium phosphate and nearly one-fourth of calcium and 

 magnesium phosphate, while another portion of phosphoric acid 

 present in that ash is derived from the destroyed nuclein and small 

 portions of lecithin/' 



The requirements for normal field crops are considerable, a wheat 

 crop, for example, extracting from 1 hectare (about 2.5 acres) of 

 ground about 26.5 kilos of this acid. The forest products require 

 much less. It is in the production of seeds especially that the pow- 

 erful influence of fertilization with phosphates becomes apparent. 



a Several views have been expressed as to the transportation of calcium phosphate 

 to the seeds. This salt is insoluble in water, but may be dissolved in small quantities 

 by the weak acid juices of the plant. Vaudin (Chem. Zeitung, No. 91, 1895) believes 

 that its transportation in the vegetable organism is accomplished by sugar and potas- 

 sium maiate or citrate, which dissolve it in small quantities. 



