HARDWICKE'S SCIENCE-GOSSIP. 



we melt it, and allow it to cool to about 100°, and 

 then, while it is still soft and viscid, we rapidly 

 and frequently extend and double it up. The tem- 

 perature of the mass quickly rises to 140° or up- 

 wards, and after this evolution of heat the sugar is 

 found on cooling to be in the condition, not of a 

 glass, but of minute crystals. 



Phosphorus is another substance which is suscep- 

 tible of a somewhat similar change. At ordinary 

 temperatures it is a clear, colourless body, 

 which melts into a liquid when heated to about 

 113° F., and readily catches fire at comparatively 

 low temperatures when exposed to the air. In 

 an atmosphere of a gas with which it does not 

 combine, it may however be heated to a temperature 

 of 460" or higher, and then the translucent liquid 

 phosphorus forms a red deposit, which is nothing else 

 than another modification of phosphorus. 



This allotropic phosphorus, as it is called, may 

 also be prepared by dissolving ordinary phosphorus 

 in bisulphide of carbon along with a small quantity of 

 iodine, and heating the solution to 212° in a sealed 

 tube for some time. The red phosphorus is then 

 precipitated from the solution in proportion as it is 

 formed. 



The difference in the appearance of the two modi- 

 fications of phosphorus is obvious. They are known 

 to differ also in most of their properties ; thus they 

 are not soluble in the same menstrua ; the liquids 

 which will dissolve one generally failing to dissolve 

 the other. The density of ordinary phosphorus is 

 1*83, while that of the red modification is 2T ; the 

 temperatures at which they respectively ignite are 

 also very widely separated. Notwithstanding all 

 these and other differences betweeu them, they are 

 mutually convertible. The red variety is prepared 

 from ordinary phosphorus, and may be converted 

 into the latter again by simply heating it to the 

 temperature at which it evaporates, and condensing 

 the vapour. Their properties are in many respects 

 less alike than those of gold and platinum ; yet we 

 do not hesitate to pronounce the substance of both 

 identical. What then causes the difference ? 



In the case of phospborus, and several other 

 bodies which are susceptible of similar changes, we 

 have not far to seek for the answer. The difference 

 in the properties of the ordinary and of the allo- 

 tropic modifications of phosphorus, is due to the 

 different quantities of heat that are present in a 

 latent form in the one aud in the other. It is not 

 usual to speak of heat as a constituent of bodies, but 

 there can be nothing better established than that its 

 presence is the modifying element in these cases. 

 I might give many proofs of this, but it may be 

 sufficient to mention that in the preparations of red 

 phosphorus by the action of iodine, Brodie found 

 that on heating the mixture of ordinary phosphorus 

 and iodine to 390°, a sharp explosion took place, 

 with a loud report, while nearly the whole of the 



phosphorus used was found to have passed into the 

 allotropic or red modification. In short, ordinary 

 phosphorus in passing into the red condition sets 

 free its combined heat, which then becomes 

 sensible. 



Among bodies derived from the organic world 

 there is a group, known as the glycerine compounds, 

 of the series of acids to which formic, acetic, and 

 other acids of the general type (C H H 2 )0. 2 belong. 

 I know that several, and I believe that all, of the gly- 

 cerine compounds of these acids, as met with in nature, 

 are susceptible of different allotropic modifications, 

 such as those we have been speaking of. Chemistry 

 is familiar with some twenty of these acids, and 

 upon good grounds presumes the existence of a great 

 many more cf them. In the whole domain of modern 

 chemistry there is no group of bodies equal to these 

 acids, and their connections, for interest and in- 

 struction. It were out of the scope of my present 

 remarks, however, to enter upon a discussion of their 

 chemical relations generally, but I may just mention 

 that corresponding to each of the acids of this series 

 there are an alcohol, an ether, an aldehyde, and 

 other bodies, each of which bears a definite relation 

 as represented by its chemical constitution, to the 

 corresponding terms {uologues) of all the other 

 series. This is readily seen from the following 

 formulae of a few isologous terms of three of the 

 series : — 



Acids. Alcohols. Ethers. 



Acetic .... C 2 H 4 2 *C 2 H 6 *C 4 H 5 



Propylic... C 3 H 6 2 C 3 H 8 C 6 H O 



Butylic... C 4 H 8 2 C 4 H 10 C 8 H 5 



Amylic .... C 5 H I0 2 C,H 12 C^H^O 



Cetylic .... C 16 H 32 2 C 1G H 34 C 32 H 33 

 Stearic C 18 R 3(i 2 t 



* * * 



Melissic .. C 30 H G0 2 C 30 H 62 0J. 



One of the most wonderful and interesting facts 

 revealed by chemistry is that to each addition of 

 this carbo-hydrogen (CH 2 ), corresponds a definite 

 alteration of physical properties, such as specific 

 heat and boiling-point. The more remote members 

 of each series differ, as may be supposed, consider- 

 ably from one another, yet they have all so much in 

 common that it mny be said — 



Facies non omnibus una, 

 Nee diversa tamen ; qualem decet esse sororum. 



I think these few remarks upon the chemical 

 characters and relations of the substances that I 

 have now to speak of will not appear to be an 

 uncalled-for digression, when it is borne in mind 

 that it is upon their territory that the science of 



* Vinous. 



t The alcohol and ether of this term have not yet been 

 actually isolated. 



X Ether not yet isolated. 



