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Chemical activity

The chemistry of the laboratory and the chemistry of protoplasm present certain contrasting features. A chemist reaches the compound which he wishes to form by effecting a series of interchanges. For example, he wishes to form uric acid by uniting a nucleus contained in lactic acid with urea. First he introduces chlorine and ammonia into the molecule of lactic acid. He makes trichlorlactamide. Then he heats (supplies energy to) a mixture of trichlorlactamide and urea. Two of the chlorine atoms carry off hydrogen atoms from the urea. A third leaves the trichlorlactamide with its ammonia. Water also breaks away. Uric acid remains.

Trichlorlactamide Urea Uric Acid CCl₃CH.OH.CO.NH₂+ 2(NH₂)₂CO= C₅H₄N₄O₃ +NH₄Cl +2HCl +H₂O.

In this example the trichlorlactamide may be said to exchange its chlorine and ammonia for urea. When he planned the reaction, the chemist foresaw what would happen. He knew that if he weakened the grip of the lact radicle upon them, chlorine and hydrogen, chlorine and ammonia, oxygen and hydrogen, would take the opportunity of getting away together. The lact radicle and urea would be left with dangling arms, which must “satisfy their affinities” by linking up. It would be rash to assert that any reaction is impossible to Nature’s chemistry; but it may safely be said that the reactions which protoplasm effects are, so far as we know them, of a different type from this laboratory example. Uric acid is the chief excrement of birds. It is made in the liver. If the liver is shut off from the circulation, lactate of ammonia is excreted in the place of uric acid. It is therefore, in all probability, lactate of ammonia which the liver transforms into uric acid. We cannot pretend to say how this is done, although an empirical formula for the change might be drafted easily enough.