24 CHEMISTRY AND PHYSICS IN RELATION 



CAUSES OF THE CHANGE OF FORM AND PROPERTY OF MATTER. 



A change of place or position in the most minute particles of a number of 

 compound substances, and their decomposition, or conversion into new products 

 may be called forth by chemical action, by heat, or electricity ; and it may also 

 be occasioned by a transference of some condition of motion, or by contact with a 

 body, the particles of which are undergoing a change of place. 



CONTINUANCE OF THE DECOMPOSITION. 



If, from any external cause by contact with oxygen, &c. the condition of 

 equilibrum in the attractive force of the elements of one of these compound atoms 

 be disturbed, the result is the establishment of a new condition of equilibrium. 

 The motion imparted to the first molecule is transferred to the second, the third, 

 &c., of the parts of similar nature, extending even to all dissimilar particles, and 

 to all other substances, if the force which held together their elements in their 

 original form and character be less than that acting upon them with an opposite 

 tendency. Want of power to maintain an original condition is want of power of 

 resistance. Every body which is capable of offering this degree of resistance, 

 hinders putrefaction and fermentation in most cases by entering into a chemical 

 combination with the body susceptible of either of these conditions ; and the power 

 of maintaining the original mode of arrangement is strengthened by every new 

 accession of the force of attraction. To the force which maintains the condition 

 of the first body, is added a second attraction which must be overcome before the 

 elements of the first can change their locality or size. 



ANTISEPTIC SUBSTANCES. 



Amongst the substances which counteract putrefaction and fermentation we must 

 mention before others, sulphurous and arsenious acids ; further, many mineral 

 acids, metallic salts, empyreumatic substances, volatile oils, alcohol, and common 

 salt. 



These substances exercise a very unequal influence upon putrid matter. Alcohol 

 and common salt in certain quantities arrest putrefaction, and consequently the 

 process of fermentation, by removing from the putrid body a certain quantity of 

 water, which is a necessary requirement for this change, Sulphurous acid, which 

 is capable of entering into combination with all organic matters generally, and 

 therefore, with all bodies susceptible of putrefaction, hinders this process on the 

 same principles. 



RELATION OF ARSENIOUS ACID TO MEMBRANES. 



Arsenious acid does not exert the smallest influence upon the fermentation of 

 sugar in the juices of plants, or upon the action of yeast on sugar: (Schloss- 

 berger.) Neither does it affect the putrefaction of the blood, but its action on 

 membranes and the membranous structures is unquestionable. Whilst a bladder, 

 or a bit of membrane covered with water is thoroughly decomposed and liquefied, 

 giving off, in the course of six weeks or less, a most offensive stench, another 

 piece of membrane or bladder likewise in contact with water will remain un- 

 changed and without smell, if arsenious acid have been added to the fluid ; the 

 explanation of this difference is, that the gelatinous tissue enters into combination 

 with the arsenious acid in the same manner as skin combines with tannic acid. 



