CARBON DIOXID 22$ 



Two grams are placed in a tared platinum crucible, which, 

 with its lid, is placed in an air bath at 105 and heated for at 

 least three hours. The lid is then put on, and the crucible is 

 placed in a desiccator and weighed as soon as cold. The loss in 

 weight is the moisture. The organic matter is determined as 

 below. 



Wyatt recommends that two grams of the fine material be 

 heated in ground watch-glasses, the edges of which are separated 

 so as to allow the escape of the moisture. 82 The heating is con- 

 tinued for three hours at 110, the watch-glasses then closed 

 and held by the clip, cooled in a desiccator, and weighed. This 

 method is excellent for very hygroscopic bodies, but where quick- 

 acting balances are used, scarcely necessary for a powdered 

 mineral. 



The residue from the moisture determination is brought into 

 a platinum crucible and gradually heated to full redness over a 

 bunsen, and then ignited over the blast-lamp. This operation is re- 

 peated after weighing until a constant weight is obtained. The loss 

 (after deducting the percentage of carbon dioxid as found in 

 another portion) may be taken as water and organic matter. 

 This method is sufficient for all practical purposes, but when 

 minerals containing fluorin are strongly ignited, a part of the 

 fluorin is expelled; hence, if more accurate determinations are 

 required, the loss of fluorin must be taken into account. It has 

 been proved that a pure calcium fluorid undergoes progressive 

 decomposition at a bright red heat with formation of lime. 



195. Carbon Dioxid. Many forms of compact apparatus have 

 been devised for this estimation, but none of them is more satis- 

 factory than Knorr's apparatus, described in Volume I. Many 

 phosphates must be heated to the boiling point with dilute acid 

 to effect complete decomposition of the carbonates. The dis- 

 tillation method described by Gooch is excellent, and when 

 once the apparatus is set up its work will be found to be rapid 

 and satisfactory. 83 



Wyatt regards the estimation of carbon dioxid as one of the 



M Phosphates of America, 4th Edition, 1892 : 144. 

 83 U. S. Geological Survey, Bulletin 47, 1888 : 16. 



