Sunday, December 21, 2014

21 December - Chemistry Knowledge History

John Mayow baptized 1641 (birth date uncertain): discovered that air contained two gases, one of which ("spiritus nitro-aerous") supported life and combustion.

Hermann Joseph Muller born 1890: theory of genes; mutation by X-rays; Nobel Prize (medicine), 1946.

December - Chemistry Knowledge History

John Mayow's Scientific Work

Mayow published at Oxford in 1668 two tracts, on respiration and rickets,

Accepting Boyle's experiments and theory that air is necessary for combustion, Mayow showed that fire is supported not by the air as a whole but by a more active and subtle part of it. This part he called "spiritus igneo-aereus," or sometimes "nitro-aereus", In combustion the nitro-aereae  supplied by the air combined with the material burnt.  Mayow observed  that antimony, strongly heated with a burning glass, undergoes an increase of weight  and he attributed it  to nothing else but these particles.

Mayow argued that the same particles are consumed in respiration, because he found that when a small animal and a lighted candle were placed in a closed vessel full of air the candle first went out and soon afterwards the animal died. However, if there was no candle present the animal lived twice as long. He concluded that this constituent of the air is absolutely necessary for life, and supposed that the lungs separate it from the atmosphere and pass it into the blood. Mayow also came out with the idea that muscles work or contract due to combination of nitro aereus  with other combustible (salino-sulphureous) particles in the body; hence the heart, being a muscle, ceases to beat when respiration is stopped. Heat in animals is due to the union of nitro-aerial particles, breathed in from the air, with the combustible particles in the blood, and it occurs in muscles during violent exertions.

In effect, therefore, Mayow gave a remarkably correct anatomical description of the mechanism of respiration and argued for the existence of oxygen, under the guise of his "spiritus nitro-aereus," as a separate entity distinct from the general mass of the air. Mayow perceived the part "spiritus nitro-aereus" plays in combustion and in increasing the weight of the calces (oxides) of metals as compared with metals themselves. Mayow described inspiration a mechanism for introducing oxygen into the body, where it is consumed for the production of heat and muscular activity. He even vaguely conceived of expiration as an excretory process. Using bell-jars over water Mayow showed that the active substance - nitro-aereus that we today call oxygen constitutes about a fifth part of the air.

Mutation of genes

Genes mutate due to thermal agitations. One gene may mutate but others around may remain stable.
Therefore high energy radiation can produe gene mutations.

Read Muller's Nobel Lecture on Mutation of Genes

December Month Chemistry Knowledge History

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