236 On the Composition of some Deep-Sea 



The dried portion was broken up in an agate mortar, and 

 preserved in a well-stoppered bottle. Sufficient quantities of 

 each sample were thus prepared in a uniform manner, and the 

 bottles in which they were preserved were carefully weighed 

 and kept under a bell-jar. In this way any alteration in the 

 substance is at once detected. If this precaution be not taken 

 it is necessary, in dealing with substances which are more 

 or less hygroscopic, to weigh out at once all the portions of 

 any one sample which will be required for the various deter- 

 minations which are to be made, in order to be certain that a 

 uniform material is used for each. This is attended with much 

 inconvenience, which is obviated by preserving the sample in 

 such a way that it will be unlikely to alter, and by keeping 

 strict account of its weight, so as at once to detect any alteration 

 which may occur. 



TABLE III. Determination of Loss on Ignition, and of 

 the Water and Carbonic Acid expelled thereby. 



Table III. Determination of the Moisture, Carbonic Acid, 

 and Total Loss. A quantity of the substance was weighed into 

 a porcelain boat, placed in a combustion tube, and heated 



