148 



THE AMEKICAN MONTHLY 



[August, 



place wlien the acid is added, lime 

 IS probably present ; the operation 

 must be continued until the effer- 

 vescence ceases. 



Wash out the acid with filtered 

 water, and proceed as in 8. (After 

 some experience the operator will 

 be able to judge whether the pro- 

 cess described in 8 will be sufficient 

 to complete the cleaning, or whether 

 he may neglect it entirely and pro- 

 ceed with 9.) 



8. Boil the moist material from 

 T with strong nitric acid, as de- 

 scribed in operation 2 (page 109). 

 In case it is not deemed necessary 

 to proceed with 9, the boiling 

 should be thorough, and the crys- 

 tals of potassic chlorate should al- 

 ways be used (2). If much organic 

 matter is present, it is always ad- 

 visable to make use of considerable 

 chlorate, and then to proceed with 

 9. Wash out the nitric acid, and 

 if the material is quite dark in 

 color, and seems to have much or- 

 ganic mattter mingled with it, it 

 should be dried; however, if it 

 seems to be quite free from organic 

 matter, the drying is not necessary, 

 although the writer usually prefers 

 to do it. Proceed with operation 9. 



9. This is the ffnal operation, and 

 if carefully conducted, is sure to be 

 successful in destroying every trace 

 of organic matter. 



The residue from 8, or in some 

 eases the raw material, preferably in 

 the dry condition, is placed in a large 

 test-tube, or in what is much better, a 

 porcelain evaporating dish, with a 

 glass funnel inverted over it for a 

 cover, to prevent spattering. Pour 

 over the mass, enough strong sul- 

 phuric acid to more than cover it, 

 and heat until dense, white fumes 

 are given off. Then raise the fun- 

 nel and add crystals of potassic 

 chlorate, cautiously from time to 

 time, and continue the additions 

 until the mass becomes of a clear, 



white color. The entire operation 

 should not take over fifteen minutes, 

 for any specimen. 



When there is considerable or- 

 ganic matter present, the first ef- 

 fect of heating the acid is to char, 

 or carbonize it ; and when this 

 takes place, it often seems impossi- 

 ble to succeed with the oxidation. 

 Consequently, if the acid begins to 

 blacken or to become discolored 

 before the dense white fumes ap- 

 pear, a few crystals of the chlorate 

 should be added immediatel}'^, but 

 do not add more than are necessary 

 to prevent the blackening, until the 

 acid becomes very hot. This diffi- 

 culty will not be encountered, if 

 the chlorate is used in sufficient 

 quantity in operation 8. 



By following these directions, 

 and using only sulphuric acid of 

 the full strength (pure commercial 

 acid), there will be no danger of 

 forming the very insoluble com- 

 pound, which troubles many who 

 attempt to work this process. 



Allow the acid to become per- 

 fectly cool, and then pour it slowly 

 into a large volume of filtered 

 water in a glass beaker, stirring the 

 water constantly with a glass rod. 

 Do not pour the water into the 

 acid, for the heat produced by their 

 combination, might crack the dish. 



10. Wash the mass in the beaker 

 until every trace of acid is removed, 

 then proceed as in operation 4 

 (p. 109). 



The principal advantage which 

 the sulphuric acid process possesses 

 over all others, is its powerful ox- 

 idizing action. The high tempera- 

 ture at which sulphuric acid boils, 

 enables us to make use of the 

 chlorate under much better con- 

 ditions than in any other process ; 

 and the acid itself dissolves the last 

 traces of iron and alumina, that may 

 have remained after the previous 

 operations. 



