ANALYSIS. 



rs produced. To ascertain its quantity, it 

 must be collected in the same manner as other 

 solid precipitates, and heated red ; the result 

 is oxide of iron, which may be mixed with a 

 little oxide of manganese. 



Into the fluid freed from oxide of iron a 

 solution of neutralized carbonate of potash 

 must be poured till all effervescence ceases in 

 it, and till its taste and smell indicate a consi- 

 derable excess of alkaline salt. The precipi- 

 tate that falls down is carbonate of lime : it 

 must be collected on the filter, and dried at a 

 heat below that of redness. The remaining 

 fluid must be boiled for a quarter of an hour, 

 when the magnesia, if any exist, will be pre- 

 cipitated from it, combined with carbonic 

 acid, and its quantity is to be ascertained in 

 the same manner as that of thAarbonate of 

 lime. If any minute proportion of alumina 

 should, from peculiar circumstances, be dis- 

 solved by the acid, it will be found in the pre- 

 cipitate with the carbonate of lime ; and it 

 may be separated from it by boiling it for a 

 few miiiutrs with soap-lye, sufficient to cover 

 the solid matter: this substance dissolves alu- 

 mina, without acting upon carbonate of lime. 



Should the finely divided matter be suffi- 

 ciently calcareous to effervesce very strongly 

 with aculs, a very simple method may be 

 adopted for ascertaining the quantity of carbo- 

 nate of lime, and one sufficiently accurate in 

 all common cases. 



Carbonate of lime (chalk) in all its states 

 contain*- a determinate proportion of carbonic 

 acid, ?. e nearly 43 per cent. ; so that when the 

 quantity of this elastic fluid given out by 

 any soil during the solution of its calcareous 

 matter in an acid is known, either in weight or 

 measure, the quantity of carbonate of lime 

 m;ty be easily discovered. 



When the process by diminution of weight 

 is employed, two parts of the acid and one 

 part of the matter of the soil must be weighed 

 in two separate bottles, and very slowly mixed 

 tcjj'tluM- till the effervescence ceases. The 

 dilll'icnce between the weight before and after 

 the experiment denotes the quantity 01 carbonic 

 acid lost: for every 4 grains of which 10 

 grain> t carbonate of lime must be estimated. 



6. After the calcareous parts of the soil have 

 been acted upon by muriatic acid, the next 

 process is to ascertain the quantity of finely 

 divided insoluble animal and vegetable matter 

 that it contains. This may be done with suf- 

 ficient precision, by strongly igniting it in a 

 crucible over a common fire till no blackness 

 remains in the mass. It should be often stirred 

 with a metallic rod, so as to expose new sur- 

 faces continually to the air : the loss of weight 

 that it undergoes denotes the quantity of the 

 substance that it contains destructible by fire 

 and air. 



It is not possible without very refined and 

 difficult experiments, to ascertain whether this 

 substance is wholly animal or vegetable mat- 

 ter, or a mixture of both. When the smell 

 emitted during the incineration is similar to 

 that of burnt feathers, it is a certain indication 

 of some substance, either .animal, or analo- 

 gous to animal matter, and a copious blue 

 flasne at the time of ignition almost always de- 



ANALYSIS. 



notes a considerable proportion of vegetable 

 matter. In cases when it is necessary that the 

 experiment should be very quickly performed, 

 the destruction o.f the decomposible substances 

 may be assisted by the agency of nitrate of 

 ammonia, which at the time of ignition may 

 be thrown gradually upon the heated mass, in 

 the quantity of 20 grains for every 100 of 

 residual soil. It accelerates the dissipation of 

 the animal and vegetable matter, which it 

 causes to be converted into elastic fluids, and 

 it is itself, at the same time, decomposed and 

 lost. 



7. The substances remaining after the de- 

 struction of the vegetable and animal matter 

 are generally minute particles of earthy matter 

 containing usually alumina and silica, with 

 combined oxide of iron or of manganese. To 

 separate these from each other, the solid mat- 

 ter should be boiled for two or three hours 

 with sulphuric acid, diluted with four times 

 its weight of water ; the quantity of the acid 

 should be regulated by the quantity of solid 

 residuum to be acted on, allowing for every 

 100 grains two drachms, or 120 grains of 

 acid. 



The substance remaining after the action of 

 the acid may be considered as silicious, and it 

 must be separated and its weight ascertained, 

 after washing and drying in the usual manner. 

 The alumina, and the oxide of iron and man- 

 ganese, if any exist, are all dissolved by the 

 sulphuric acid : they may be separated by 

 succinate of ammonia added to excess, which 

 throws down the oxide of iron, and by soap-lye, 

 which will dissolve the alumina, but not the 

 oxide of manganese : the weights of the ox- 

 ides ascertained after they have been heated to 

 redness will denote their quantities. 



Should any magnesia and lime have escaped 

 solution in the muriatic acid, they will be found 

 in the sulphuric acid: this, however, is rarely 

 the case ; but the process for detecting them 

 and ascertaining their quantities is the same in 

 both instances. The method of analysis by 

 sulphuric acid is sufficiently precise for all 

 usual experiments ; but if very great accuracy 

 be an object, dry carbonate of potash must be 

 applied as the agent, and the residuum of the 

 incineration (6.) must be heated red for half 

 an hour, with four times its weight of this sub- 

 stance in a crucible of silver, or of well baked 

 porcelain. The mass obtained must be dis- 

 solved in muriatic acid, and the solution evapo- 

 rated till it is nearly solid ; distilled water must 

 then be added, by which the oxide of iron and 

 all the earths except silica will be dissolved 

 in combination as muriates. The silica after 

 the usual process of lixiviation must be heated 

 red : the other substances may be separated in 

 the same manner as from the muriatic and 

 sulphuric solutions. This process is the one 

 usually employed by chemical philosophers 

 for the analysis of stones. 



8. If any saline matter, or soluble vegetable 

 or animal matter, is suspected in the soil, i 

 will be found in the water of lixiviation used 

 for separating the sand. This water must be 

 evaporated to dryness in a proper dish, at a 

 heat below its boiling point. If the solid matter 

 obtained is of a brown colour and inflamma 



H 85 



