THE ASH CONSTITUENTS OF PLANTS. 



211 



ducted, and with an arrangement for retaining any particles of volatil- 

 ized .sid).stan('e. The construction of the two forms of apparatus is 

 shown in the accompanying figures. 



A weighed amount of the substance is placed in the crucible without 

 the cover, and charred on a sand l)ath until no more gases are given 

 off. The cover with the tube for conducting air is then put in place 

 and the crucible heated over a naked flame. The air is forced into 

 the Shuttleworth apparatus (see fig. 1), while in the Tucker apparatus 



Fig. 1. — Shuttleworth apparatus for ash determination. 



(fig. 2) it is drawn through b}^ means of an aspirator, the tube conducting 

 the current of air to the bottom of the crucible carrying a stirrer in 

 both cases. In the Shuttleworth apparatus the loss of light particles 

 of matter is avoided by an attachment to the cover (cf, !>,) contain- 

 ing water (c). In the Tucker apparatus the air drawn off is passed 

 through a small flask {g) containing water, in which the volatilized 

 chlorids, etc., are collected. 



During the combustion the substance is stirred by a platinum stirrer, 



