132 Transactions of the South African Philosophical Society. 
minutes, and after cooling the liquid is filled up to the mark with dis- 
tilled water and filtered into a suitable bottle. This filtered soil extract 
is then employed for the actual estimations of lime and potash.* 
For the determination of lime 50 c.c. of the extract (equal to 25 
grammes of soil) are removed by means of a pipette into a 250 c.c. 
boiling flask: after adding two or three drops of rosolic acid solution, 
ammonia is added very carefully by means of a dropping tube until 
a pinkish colour makes its appearance in the supernatant liquid. It 
is then boiled until the pink colour almost disappears again, the 
alumina and oxide of iron being thus precipitated. After cooling 
the flask is filled up to the mark, thoroughly shaken, and the con- 
tents filtered into a 300 c.c. bottle. One hundred c.c. of this clear 
filtrate (equal to 10 grammes of soil) are removed by a pipette into a 
300 ¢.c. Erlenmeyer flask; three to five drops of acetic acid are added 
and 20 c.c. of a 4 per cent. ammonic oxalate solution. The mixture 
is placed on a water oven for six hours and then filtered through 
double filter papers. The precipitate on the filters is ignited at first. 
over a Bunsen flame and is then strongly heated in a furnace for ten 
minutes. After cooling it is weighed and the lime calculated as CaO. 
In determining potash another 50 c.c. of the filtered soil extract: 
is placed in a 250 c.c. flask and boiled. Five c.c. of a 10 per cent. 
solution of baric chloride are added, and the mixture is boiled for 
‘some time for the precipitation of sulphuric acid. A few drops of 
rosolic acid are next added, and the mixture is boiled with ammonia 
as in the case of the lime determination. When partly cooled down 
‘2 or 3 grammes of crystalline ammonic carbonate are added, 
and the temperature is once more raised to boiling-point in order to 
separate lime and barium. After complete precipitation of the 
latter the liquid is cooled, the flask filled up to the mark, and the 
contents filtered. Of this filtrate 100 c.c. (equivalent to 10 grammes. 
of soil) are placed in a platinum basin and heated to dryness on a 
water bath. The dish containing the residue is heated on asbestos 
sheet and then carefully over a small open flame until all ammonium 
salts have been expelled. The residue is then washed through a 
filter with boiling water into a glass dish. Two c.c. of a 10 per 
cent, solution of platinic chloride are added, and the mixture is 
evaporated to dryness on the water bath. After cooling, some 
dilute alcohol (81 to 82 per cent.) is added to the residue, and it is 
allowed to stand for at least half an hour, It is now filtered 
through a Gooch crucible by aid of a filter pump, washed first with 
* It should be observed that the soils from the Riversdale and Mossel Bay 
Divisions were extracted by means of a modified process, The results in’ these 
cases are hence not quite on all fours with the others, and due allowance should 
be made in comparing them. 
