CARBON AND THE HYDROCARBONS 855 



solid substances of organisms, contain a store or accumulation of 

 internal power in the form of the energy binding the atoms into complex 

 molecules. When charcoal or complex compounds of carbon burn, the 

 energy of the carbon and oxygen is turned into heat, and this fact is 

 taken advantage of at every turn for the generation of heat from fuel. 20 

 No other two elements are capable of combining together in 

 such variety as carbon and hydrogen. The hydrocarbons of the 

 CJEE 2m series in many cases differ widely from each other, although 

 they have some properties in common. All hydrocarbons, whether 

 gaseous, liquid or solid, are combustible substances sparingly soluble or 

 insoluble in water. The liquefied gaseous hydrocarbons, as well as those 

 which are liquid at ordinary temperatures, and those solid hydrocarbons 

 which have been liquefied by fusion, have the appearance and property 

 of oily liquors, more or less viscid, or fluid. 21 The solid hydrocarbons 

 more or less resemble wax in their properties, although ordinary oils 



The endeavours which have been directed towards determining the measure 

 of complexity of the molecules of charcoal, graphite, and the diamond will probably at 

 some period lead to the solution of this problem and will most likely prove that the 

 various forms of charcoal, graphite, and the diamond contain molecules of different and 

 very considerable complexity. The constancy of the grouping of benzene, C 6 H 6 , and the 

 wide diffusion and facility of formation of the carbohydrates containing CQ (for example, 

 cellulose, C 6 H 10 O 5 , glucose, C 6 H 12 O 6 ) give reason for thinking that the group C 6 is the 

 first and simplest of those possible to free carbon, and it may be hoped that some time 

 or other it may be possible to get carbon in this form. Perhaps in the diamond there 

 may be found such a relation between the atoms as in the benzene group,, and in charcoal 

 such as in carbohydrates. 



20 When charcoal burns, the complex molecule C n is resolved into the simple mole- 

 cules nCOj, and therefore part of the heat probably no small amount is expended in 

 the destruction of the complex molecule C n . Perhaps by burning the most complex 

 substances, which are the poorest as regards hydrogen, it may be possible to form an 

 idea of the work required to split up C n into separate atoms. 



21 The viscosity, or degree of mobility, of liquids is determined by their internal 

 friction. It is estimated by passing the liquids through narrow (capillary) tubes, the 

 mobile liquids passing through with greater facility and speed than the viscid ones. The 

 viscosity varies with the temperature and nature of the liquids, and in the case of solu- 

 tions changes with the amount of the- substance dissolved, but is not proportional to it. 

 So that, for example, with alcohol at 20 the viscosity will be 69, and for a 50 p.c. solu- 

 tion 160, the viscosity of water being taken as 100* The volume of the liquid which 

 passes through by experiment (Poiseuille) and theory (Stokes) is proportional to the 

 time, the pressure, and the fourth power of the diameter of the (capillary) tube, and 

 Inversely proportional to the length of the tube ; this renders it possible to form com- 

 parative estimates of the coefficients of internal friction and viscosity. 



As the complexity of ihe molecules of hydrocarbons and their derivatives increases 

 by the addition of carbon (or CH 2 ), so does the degree of viscosity also rise. The exten- 

 sive series of investigations referring to this subject still await the necessary generalisa- 

 tion. That connection which (already partly observed) ought to exist between the 

 viscosity and the other physical and chemical properties, forces us to conclude that the, 

 magnitude of internal friction plays an important part in molecular mechanics. In 

 investigating organic compounds and solutions, similar researches ought to stand fore- 

 most. Many observations have already been made, but not much has yet been done 



