No. v.] OP THE SOLUBLE SALINE MATTER IN THE SOIL. 35 



If no precipitate fall, oxalate of ammonia is to be added as long as any white 

 powder appears to be produced. The solution must then be left to stand over 

 night — that the whole of the lime may separate,- the white powder afterwards 

 collected on a filter, washed, driel, and burned with the filter, at a low red heat. 

 The grey powder obtained is carbonate of lime, every 100 grs. of which con- 

 tain 43'71 grs. of lime. 



d. Esliniatinn of the O.vi.ie of Iron mid of the Aluviina. — But if a precipitate 

 fall on the addition of ammonia, as above prescribed — the solution may con- 

 tain magnesia, alumina, and the oxides of iron, and manganese. In this case 

 the precipitate is to be re-dissolved by the addition of muriatic acid till it is dis- 

 tinctly acid, and ammonia again added in slight excess. If any precipitate now 

 fall, it will consist only of alumina and oxide of iron, unless magnesia and 

 oxide of manganese be present in large proportion, when a minute quantity of 

 each may fall at the same time. 



The precipitate is to be collected on the filter as quickly as possible, — the fun- 

 nel being at the same time covered with a plate of glass to prevent as much as 

 possible the access of the air, — washed with distilled water, and then re-dissolved 

 in muriatic acid. This is best effected by spreading out the filter in a small 

 porcelain dish, adding dilute acid till all is dissolved, and then washing the pa- 

 per well with distilled water, A few drops of nitric acid are then to be added, 

 and the solution heated, to peroxidize the iron. A solution of caustic potash 

 added in excess will at first throw down both the oxide of iron and alumina, but 

 will afterwards re-dissolve the alumina, and leave only the oxide of iron. This 

 is to be collected on a filter, washed, dried, heated to redness, and weighed. 

 Every 100 grains of this peroxide of iron are equal to 89*78 grains of protoxide, 

 in which state it had most probably existed in the original solution. 



To the potash solution muriatic acid is added till the alkali is saturated, or till 

 the solution reddens Utmvs paper * when the addition of ammonia precipitates 

 the alumina. A s it is difficult to wash this precipitate perfectly free from potash, it 

 is better to dissolve it again in muriatic acid, and to re-precipitate it by caustic 

 ammonia. When well washed, dried, and weighed, this precipitate gives the true 

 quantity of alumina present in the portion of salt submitted to analysis. 



e. Estiniatioih of the Manganese. — To the ammoniacal solutions from which 

 the oxalate of lime has been precipitated ('■), a solution of hydro-sulphuret of 

 ammonia is to be added. The manganese will fall in the form of a flesh red 

 sulphuret. When this precipitate has fully subsided, it must be collected on the 

 filter and washed with water containing a very little hydro-sulphuret of ammo- 

 nia. The filter is then put into a glass or porcelain basin, the precipitate dis- 

 solved off by dilute muriatic acid, and the solution filtered, if necessary. A so- 

 lution of carbonate of potash then throws down carbonate of manganese, which 

 is collected, dried, and heated to redness in the air. Of the brown powder ob- 

 tained 100 grains indicate the presence of 93'84 grains of protoxide of manganese 

 in the salt or solution under examination. 



/. Estimation of the Magnesia. — If no potash or soda be present in the residual 

 solution, the determination of the magnesia is easy. A few drops of muriatic 

 acid are added, and the whole gently heated, and afterwards filtered, to separate 

 the sulphur of the excess of hydro-sulphuret of ammonia previously added. The 

 solution is then evaporated to dryness, and the dry mass heated to redness to 

 drive off all the ammoniacal salts previously added. A few drops of diluted sul- 

 phuric acid are added to what remains, to change the whole of the magnesia 

 into sulphate, the mass again heated to redness and weighed. One hundred 

 grains of this sulphate indicate the presence of 3401 grs. of pure magnesia. 



But if potash or soda be present — the weight of which it is desirable to deter- 

 mine — the simplest method is to take a fresh portion, 15 to 20 grains, of the 



* Litmus paper is paper stainetl by dipping it into a soluUta of litmus, a vegetable blue co 

 lour, prepared and sold fortl"e purpose of detecting the prt&'xice of free acids, by which it 

 is reddened. 



