The Formation of the Earth 51 



time. It was just this fact which served as a basis for N. V. Sokolov when, in 

 1890, he put forward the hypothesis that organic substances entered into the 

 composition of the Earth at the time of its formation [31a]. 



Extremely interesting evidence about the organic compounds of the planetary 

 system is provided by the study of one type of meteorites, namely the carbonaceous 

 chondrites. They are called carbonaceous because they contain amorphous 

 carbon, and possibly also graphite, as well as various hydrocarbons. Some years 

 ago Mueller [32] undertook a study of such compounds in one such meteorite 

 in the British Museum. This work is so far the most comprehensive. 



The British Museum contains specimens from all the 20 carbonaceous chon- 

 drites which are known from all over the world. It has been shown that nineteen 

 of these give no fluorescence with ultraviolet rays. This indicates the absence 

 of free hydrocarbons having a H/C ratio greater than 1-4. 



The hydrocarbons contained in the Cold Bokevelt meteorite have been 

 submitted to detailed analysis. Extraction with numerous solvents (methyl 

 alcohol, ethyl alcohol, chloroform, benzene) applied in various orders has 

 shown the extracted material to amovmt to i-i%, the greatest part being extracted 

 with ethyl alcohol and benzene. The extracted material after deduction of 

 ash (18%) and crystals of sulphur (11-12%) had the following composition: 

 C, 24-26; H, 8-12; N, 4-00; S, 878; CI, 5-89; O etc., 48-95%. 



The presence of chlorine in organic compoimds is of particular interest since 

 halogens are absent from terrestrial bitumens. 



A study of thermal breakdown at temperatures up to 350 °C showed that the 

 substances extracted lost 55% of their weight while the powdered meteorite 

 lost only 8-85% (mainly due to the loss of combined water which is present in 

 all carbonaceous chondrites). 



By comparing the carbon compounds present in the Cold Bokevelt meteorite 

 with the bituminous substances found in terrestrial sedimentary deposits, 

 Mueller noticed the following two important differences. In the first place, on 

 heating the meteorite lost water, but it did not give off liquid hydrocarbons. In 

 the second place, terrestrial carbonaceous substances are not, as a rule, extracted 

 by solvents. The first of these assertions requires confirmation as Boato [33] 

 found that, on heating powdered specimens of some carbonaceous chondrites, 

 to 250-300 "C, oily sublimates made their appearance in a number of cases. 

 Nevertheless, there is a difference between the carbonaceous compounds in 

 meteorites and the terrestrial bituminous substances, and, in particular, the 

 abiogenic origin of the meteoritic compounds is not open to the least doubt. 

 Terrestrial minerals of biological origin always give optical rotation while the 

 extracts of meteorites studied by Mueller were optically inactive. He therefore 

 made special mention of a fallacy which is often met with in popular literature, 

 namely that the presence of organic compounds in meteorites may be inter- 

 preted as indicating the presence of life on those bodies from which they ori- 

 ginated. Mueller beHeves that the meteoritic organic material consists of com- 

 plicated organic acids which arose abiogenically by a process of polymerization 

 in a gaseous medium containing nitrogen, chlorine and sulphur. Judging from 

 the difficulty of dissolving silicates, this material envelopes the stony particles. 



