THE LABORATORY. 531 



sufficiently large ; let them stand together till no 

 more effervescence takes place ; and it" it was very 

 considerable, pour in half an ounce more of the acid ; 

 let this stand also till the effervescence ceases ; if any 

 arose upon pouring it in, continue to add more acid 

 in the same manner, until what was poured in last, 

 produces little effervescence, which is often at the first, 

 and generally at the second or third half ounce. 



After the effervescence has ceased, put the whole 

 in a filter ; let the solution filtrate through ; pour half 

 a pint of water upon what remains in the filter, let 

 that filtrate also in the same vessel ; add to the solu- 

 tion thus filtrated, an ounce and a half of caustic vo- 

 latile alkali for every ounce of acid used ; if any pre- 

 cipitation take place, there is magnesia, earth of 

 alum, or the calx of a metal (generally iron or copper) 

 contained in the soil ; after adding the volatile alkali, 

 the whole is to be thrown into a filter again ; after 

 the filtration has taken place, pour into the liquor a 

 solution of mild, fixed, vegetable alkali, in water ; 

 if there be any calcareous earth in the soil, a precipi- 

 tation will take place ; continue to add the solution 

 >f the alkali till no fresh precipitation ensues ; throw 

 the whole into a filter ; let the liquor filtrate off; pour 

 on by degrees a pint of water; let that filtrate off 

 also ; dry what remains in the filter ; it is the calcare- 

 ous earth. 



To know the proportion of sand and clay. 



Take what remains in the filter after the first solu- 

 tion in the foregoing operation, and by eliitriatiou 

 separate the sand from the clay, dry and weigh them; 

 if there be any pyrites it will appear in tiu- rand. 



M m 3 In 



