INTRODUCTORY REMARKS. 203 



4. Sodium biborate, borax, Na. 2 Bo 4 O..10H 2 O. 



5. Sodium-ammonium-hydrogen phosphate (phosphorus salt), Na(NH 4 )HPO 4 . 

 4H 2 0. 



6. Potassium carbonate, K. 2 CO 3 . 



7. Potassium nitrate, KNO 3 . 



8. Potassium chlorate, KC1O 3 . 



9. Potassium permanganate, K 2 Mn 2 O 8 . 



10. Potassium cyanide, KCy. 



11. Calcium hydrate, Ca2HO. 



12. Ferrous sulphide, FeS. 



13. Ferrous sulphate, FeSO 4 .7H 2 O. 



14. Manganese dioxide, MnO 2 . 



15. Zinc, granulated, Zn. 



16. Copper, Cu. 



17. Cupric oxide, CuO. 



18. Cupric sulphate, CuSO 4 .5H 2 O. 



19. Tartaric acid, H 2 C 4 H 4 O 6 . 



20. Starch, C 6 H 10 O 5 . 



While the apparatus and reagents here enumerated are the 

 more important ones, the analyst will occasionally require 

 others not mentioned in the above lists. 



General mode of proceeding in qualitative analysis. Every step 

 taken in analysis should be properly written down in a notebook, 

 and these remarks should be made directly after a reaction has 

 been performed, and not after the nature of the substance has 

 been revealed by perhaps numerous reactions. 



Not only the reactions by which positive results have been 

 obtained should be noted, but also those tests and reagents 

 mentioned which have been applied with negative results, that 

 is, which have been applied without revealing the presence of 

 any substance or any group of substances. Such negative re- 

 sults are, however, positive in so far as they prove the absence 

 of a certain substance or certain substances, for which reason 

 they are of direct value and should be noted. 



In comparing finally the result obtained by the analysis with 

 the notes taken during the examination, none of them should 

 be contradictory to the conclusions drawn. If, for instance, the 

 preliminary examination showed the substance to have been 

 volatilized by heating upon platinum foil with the exception of a 

 very slight residue, and if, afterwards, other tests show the presence 

 of ammonia and hydrochloric acid and the absence of every- 

 thing else, and if then the conclusion be drawn that the sub- 



