366 
VARIOUS METHODS OF ANALYSING ASHES. 
method, a circumstance which has likewise been observed by Rose 
and Weber. 
Strecker has convinced himself by experiment, that on burning 
the substances in a muffle according to Erdmann's method, any loss 
of chlorides and phosphorus can be avoided by the addition of some 
hydrate of baryta to the subtances to be incinerated.* The same 
chemist has detected in the ashes of nitrogenous substances, for 
instance of the aqueous extract of blood, of bile, &c, the presence 
of salts of cyanic acid. 
Staffel has likewise submitted Rose's method to examination, 
and has arrived at the same results as Strecker. For this reason, 
Staffel prefers the method proposed some time previously by Wack- 
enroder, but so modified that the charred mass is always first ex- 
hausted with boiling water, after which the charcoal is inciner- 
ated. According to this method, the treatment of organic sub- 
stances is divided into three parts as follows : — 
I. The organic substances dried at 86° F., are carbonized in a 
crucible, the lid of which is stuck on with starch paste. The lid 
has a hole through which the gases escape ; these are set light to. 
The charred mass is converted by pressure into a coarse powder, 
emptied into a flask, and repeatedly exhausted with boiling water 
until the liquid, which is generally transparent, leaves no percepti- 
ble residue on evaporation. When the extract is very alkaline, a 
current of carbonic acid is passed through it, after which it is eva- 
porated to dryness in a platinum crucible until the weight of the 
residue remains constant. 
The solution of the weighed residue is acidified with nitric acid. 
If, on treating the mass with nitric acid, a separation of silica oc- 
cur, it is collected on a filter and weighed. The liquid filtered 
from the silica is mixed with a solution of silver, and the chlorine 
determined from the amount of chloride of silver obtained. The 
liquid filtered from the chloride of silver is freed from the excess 
of silver by muriatic acid, and then an excess of ammonia added 
to it; if no separation of phosphate of lime occur, the ammoniacal 
* On this point Rose observes, " This certainly has many advantages. 
But the removal of a large quantity of sulphate of baryta, when lime is 
present, entails so much inconvenience, that the use of a weighed quantity 
of carbonate of soda is perhaps preferable." — Ausfuhi. Handb., vol. ii. p. 
782. 
