SOLIDIFICATION OF CARBONIC ACID. ] 



CHEMISTRY. 



827 



We need scarcely state, that great danger always attends 

 the performance of such an experiment as the conden- 

 Fig. 56. 



sation of carbonic acid gas ; and some lives have been 

 lost thereby, through the explosion of the apparatus. It 

 has been proposed to employ carbonic acid gas as a 

 mot i ve agent, in place of steam ; but the application has 

 never yet been practically adopted. 



The composition of carbonic acid gas may readily be 

 ascertained, and the presence of carbon therein proved, 

 by tilling a Florence flask with the gas, into which a 

 piece of potassium, of the size of a pea, may then be 

 dropped ; the heat of the spirit-lamp may be applied, 

 when the metal will seize the oxygen of the acid, 

 setting the carbon free as a black powder. On the 

 other hand, the presence of carbon may be proved in 

 the diamond, by burning that gem in oxygen, when 

 carbonic acid will be produced, which will at once form 

 chalk with lime-water. 



Carbon has peculiar properties of absorbing into its 

 pores gases of all kinds ; and, in every case, it has 

 highly anti-septic properties. For this purpose, it may 

 be procured from wood, cones, peat, <tc. : all that is 

 required is, that it should be highly porous. Putrefy- 

 ing animal matter may be covered, to a depth of a few 

 inches, with small pieces of wood charcoal, and no smell 

 whatever will arise from it. It has been employed by 

 Messrs. Stenhouse and Watson, as a purifier of air to 

 hospitals, <fcc., when such bindings are situated in un- 

 healthy positions. Its use as a dentifrice is well known. 

 Charcoal enters largely into the composition of gun- 

 powder ; for which purpose the best qualities are sought 

 for. The explosive effect of gunpowder and gun-cotton 

 is due to the sudden liberation of carbonic acid and other 

 gases, during the combustion of the solid materials. 



With sulphur, carbon forms a peculiar liquid, called 

 bisulphide of carbon. This is prepared by passing the 

 vapour of sulphur over pieces of charcoal heated red-hot, 

 and contained in an iron tube. Bisulphide of carbon 

 is a common product of the distillation of coals ; to 

 which reference has already been made in the article 

 on artificial illumination.* 



We must also refer our readers, for a full description 

 of the composition of fatty matters, both animal anil 

 vegetable, and the nature and composition of the pro- 

 ducts of their distillation, and that of coal in producing 

 the various combinations of carbon and hydrogen, de- 

 fiant gas, carburetted hydrogen, paraffin, (fee., to the 

 name subject ; in which they will find the fullest details. 

 Wo may, however, add, that since that portion of this 

 work has gone to press, a new source of mineral oil lias 

 been discovered in North America, which seems in- 

 exhaustible, and which promises to reduce the cost of 

 illuminating agents to a great extent. 



Carbon and Nitrogen. A very interesting series of 

 compounds is produced by the union of carbon and 

 See !:, p. 119. 



nitrogen, and bases: of these we shall first mention 

 cyanogen. 



Cyanogen is a bicarbide of nitrogen ; being composed 

 of one equivalent of nitrogen united to two of 

 carbon. Its symbol is Cy ; equivalent = 26. It 

 is obtained by heating cyanide of mercury in a 

 test-tube, fitted with a bent glass tube ; and it 

 may be collected in the usual way by means of 

 the pneumatic trough. This gas has a smell like 

 prussic acid, of which it is a constituent ; it burns 

 readily, and is highly poisonous. 



Cyanogen produces hydrocyanic, or prussic 

 acid, by uniting with one equivalent of hydro- 

 gen. Hydrocyanic acid is generally prepared 

 from the ordinary prussiate of potass, by means 

 of sulphuric acid. These materials, with water, 

 are placed in a retort, and the acid is distilled 

 over in a dilute state. It is highly poisonous; 

 has a smell like bitter almonds ; and forms salts, 

 which are commonly termed prussiates, some of 

 which we shall have to notice hereafter. Cy- 

 anogen unites with metals forming the sub- 

 stances called cyanides. These are largely em- 

 ployed in electrotyping processes ; and their 



manufacture and uses have already been exten- 



, sively dealt with under the head of Electro-Metallurgy. 

 Cyanogen also unites with sulphur, forming what is 

 termed sulpho-cyanogen and the sulpho-cyanic acid. 



The union of carbon with iron, producing steel and 

 other combinations already referred to, but not yet de- 

 scribed will be taken up in connection with the sub- 

 stances, as we examine each separately. 



OXYGEN, HYDROGEN, NITROGEN, CARBON, 

 ETC., AND THEIR FUNCTIONS IN ANIMAL 

 STRUCTURE AND SUSTENANCE. 



IN our previous pages, we have frequently remarked on 

 the different compounds on which animal life depends ; 

 and have shown that oxygen, hydrogen, nitrogen, and 

 carbon, are each necessary to the formation of animal 

 substances. We shall now proceed, by way of illus- 

 trating the laws already explained, to call attention to 

 the nature of animal organisation, and the functions 

 which the elements, already considered, exercise thereon ; 

 ami for that purpose shall avail ourselves of an able 

 article, translated by Dr. Brotmer, from the works of 

 Professor Moleschott, of Zurich. We have ventured to 

 make some alterations in those parts in the original, 

 which are more fitted for perusal by professional per- 

 sons only, or have been previously considered ; but have 

 retained all which bear on the questions we have already 

 discussed. The general reader will perceive the inti- 

 mate relationship which exists between vitality and 

 chemical action, and will also acquire a knowledge of 

 the constituents of organised substances. It will also 

 be noticed, how few are the elements which are em- 

 ployed to produce a multitude of results. These, with 

 the exception of two or three mineral substances, have 

 already passed under review. 



This subject will be again referred to when we enter 

 on the question of organic analysis ; and the perusal of 

 the succeeding article will prepare the reader for a close 

 examination of chemical facts, whilst it assists in the 

 generalisation of them. The nature of the blood is 

 first considered, with its uses in producing animal 

 tissues, ic. The author then proceeds to point out the 

 substances producing healthy and life-giving blood in 

 each kind of food ; concluding with general observations 

 on the different kinds of diet required to meet the varied 

 wants of mankind. His remarks are as follow: 



1. On the Formation of the Blood. In former times it 

 was conjectured, and, as it were, instinctively asserted, 

 that the human body changes its material and pro- 

 perties at certain epochs of life ; and this has been 

 proved to demonstration by the investigations of phy- 

 siologists during the present century. Though we cannot 

 determine whether the body is renewed entirely in seven 

 years, as is popularly believed, or in a much shorter 



