[ 824 1 



(4) Phosphates. The filtrate and washings from the 

 sand are then diluted to about 300 c. c ; Ammonium Hydrate 

 is gradually added; the filtrate being stirred with a glass 

 rod. When the precipitate settles, it is filtered through 

 ordinary filter-paper and washed on the filter several times 

 with ammonia water. The precipitate is then rinsed out 

 into a beaker, the filter-paper being afterwards thoroughly 

 washed with a little dilute HC1, the HC1 being allowed to 

 collect in the same beaker containing the precipitate. This 

 acid redissolves the precipitate. The redissolving is necessary 

 to free the phosphates from lime still further. It is again 

 diluted to about 300 c. c., ammonium hydrate is again added 

 in the same way, and the precipitate again .collected in the 

 same way on the filter-paper. It is dried in the water-oven ; 

 collected in the crucible, the filter-paper being burnt white 

 and added to the crucible. It is ignited, put inside the desic- 

 cator, and when cool, weighed. This gives the weight of a 

 portion of the phosphates in i gram of bone-meal. But as 

 Calcium Phosphate is not quite insoluble in water, all the 

 filtrates and washings are collected together in one beaker, 

 and concentrated by boiling to about 150 c. c. A little acid is 

 added to dissolve the CaCOs deposited. It is again boiled 

 to drive away the CO 2 ; and when cool, Ammonium Hydrate 

 is added gradually, and when the phosphates are deposited, 

 they are collected in filter-paper, washed thoroughly, dried 

 in water-oven, ignited in a crucible, the filter-paper being 

 burnt white and added. When cool it is weighed, and the 

 weight obtained gives the additional quantity of phosphates 

 in the i gram of bone-meal. 



(5) Calcium Carbonate. The filtrate from the phos- 

 phates is boiled with Ammonium Oxalate. The precipitate 

 is collected on Swedish filter-paper, dried in water-oven, 

 gently ignited to convert the Calcium Oxalate into CaCO 3 

 instead of into CaO. The paper ash is also added. 

 Weighed in a porcelain crucible of known weight, the 



