128 



AGRICULTURAL CHEMISTRY. 



change. Muriatic and acetic acids, and in 

 several cases nitric acid, are to be preferred 

 for this purpose before all others. Chlorine 

 also is a substance which destroys ammonia 

 and organic bodies with much facility ; but 

 it exerts such ao injurious and prejudicial 

 influence upon the lungs, that it may be 

 classed amongst the most poisonous bodies 

 known, and should never be employed in 

 places in which men breathe. 



Carbonic acid and sulphuretted hydrogen, 

 which are frequently evolved from the earth 

 in cellars, mines, wells, sewers, and other 

 places, are amongst the most pernicious mi- 

 asms. The former may be removed from 

 the air by alkalies, the latter, by burning 

 sulphur, (sulphurous acid,) or by the evapo- 

 ration of nitric acid. 



The characters of many organic com- 

 pounds are well worthy of the attention and 

 study both of physiologists and pathologists, 

 more especially in relation to the mode of 

 action of medicines and poisons. 



Several of such compounds are known, 

 which to all appearance are quite indifferent 

 substances, and yet cannot be brought into 

 contact with one another in water without 

 suffering a complete transformation. All 

 substances which thus suffer a mutual de- 

 composition, possess complex atoms ; they 

 belong to the highest order of chemical com- 

 pounds. For example, amygdalin, a con- 

 stituent of bitter almonds, is a perfectly neu- 

 tral body, of a slightly bitter taste, and very 

 easily soluble in water. But when it is in- 

 troduced into a watery solution of synaptas, 

 (a constituent of sweet almonds,) it disap- 

 pears completely without the disengagement 

 of any gas, and the water is found to con- 

 tain free hydrocyanic acid, hydruret of ben- 

 zule (oil of bitter almonds,) a peculiar acid 

 and sugar, all substances of which merely 

 the elements existed in the amygdalin. The 

 same decomposition is effected when bitter 

 almonds, which contain the same white 

 matter as the sweet, are rubbed into a pow- 

 der and moistened with water. Hence it 

 happens that bitter almonds pounded and 

 digested in alcohol, yield no oil of bitter al- 

 monds containing hydrocyanic acid, by dis- 

 tillation with water ; for the substance which 

 occasions the formation of those volatile sub- 

 stances, is dissolved by alcohol without 

 change, and is therefore extracted from the 

 pounded almonds. Pounded bitter almonds 

 contain no amygdalin, also, after having 

 been moistened with water, for that sub- 

 stance is completely decomposed when they 

 are thus treated. 



No volatile compounds can be detected by 

 their smell in the seeds of the Sinapis alba 

 and S. rug-ra. A fixed oil of a mild taste is 

 obtained from them by pressure, but no trace 

 of a volatile substance. If, however, the 

 seeds are rubbed to a fine powder, and sub- 

 jected to distillation with water, a volatile 

 oil of a very pungent taste and smell passes 

 over along with the steam. But if, on the 

 Contrary, the seeds are treated with ilcohol 



previously to their distillation w/th water, tne 

 residue does not yield a volatile oil. The 

 alcohol contains a crystalline body called 

 sinapin, and several other bodies. Those do 

 not possess the characteristic pungency of 

 the oil, but it is by the contact of them with 

 water, and with the albuminous constituents 

 of the seeds, that the volatile oil is formed. 



Thus bodies regarded as absolutely indif- 

 ferent in inorganic chemistry, on account of 

 their possessing no prominent chemical 

 characters, when placed in contact with one 

 another, mutually decompose each other. 

 Their constituents arrange themselves in a 

 peculiar manner, so as to form new com- 

 binations j a complex atom dividing into two 

 or more atoms of less complex constitution, 

 in consequence of a mere disturbance in the 

 attraction of their elements. 



The white constituents of the almonds 

 and mustard, which resemble coagulated al- 

 bumen, must be in a peculiar state in order 

 to exert their action upon amygdalin, and 

 upon those constituents of mustard from 

 which the volatile pungent oil is produced. 

 If almonds, after being blanched and 

 pounded, are thrown into boiling water, or 

 treated with hot alcohol, with mineral acids, 

 or with salts of mercury, their power to 

 effect a decomposition in amygdalin is com- 

 pletely destroyed. Synaptas is an azotised 

 body which cannot be preserved when dis- 

 solved in water. Its solution becomes 

 rapidly turbid, deposits a white precipitate, 

 and acquires the offensive smell of putrefy- 

 ing bodies. 



It is exceedingly pwobable that the pecu- 

 liar state of transposition into which the ele- 

 ments of synaptas are thrown when dis- 

 solved, in water, may be the cause of the 

 decomposition of amygdalin, and formation 

 of the new products arising from it. The 

 action of synaptas in this respect is very 

 similar to that of rennet upon sugar. 



Malt, and the germinating seeds of corn 

 in general, contain a substance called dias- 

 tase, which is formed from the gluten con- 

 tained in them, and cannot be brought in 

 contact with starch and water, without effect- 

 ing a change in the starch. 



When bruised malt is strewed upon warm 

 starch made into a paste with water, the 

 paste after a few minutes becomes quite 

 liquid, and the water is found to contain, in 

 place of starch, a substance in many respects 

 similar to gum. But when more malt is 

 added and the heat longer continued, the 

 liquid acquires a sweet taste, and all the 

 starch is found to be converted into sugar of 

 srrapes. 



The elements of diastase have at the same 

 time arranged themselves mto new combina- 

 tions. 



The conversion of the starch contained in 

 food into sugar of grapes in diabetes indi- 

 cates that amongst the constituents of some 

 one organ of the body a substance or sub- 

 stances exist in a state of chemical ac f ion, 



which the vital principle of the diseased 



