CHAPTER I. 

 GENERAL INFORMATION 



PURITY OF CHEMICALS: 



Several grades of many of the chemicals are kept in stock and care 

 must be used in issuing chemicals so that the proper quality is furnished 

 to the investigator. If there is any doubt as to the quality or quantity 

 requested, consult with the person in charge before filling the order. 



Every precaution must be taken to prevent contamination of the U.S. P. 

 and Reagent grades. The necks and caps of all reagent bottles should be 

 free from dust before the bottle is opened. Spatulas are not to be intro- 

 duced into the reagent stock bottles unless necessary, and then only after 

 they have been thoroughly cleaned and dried. Material removed is not to , 

 be returned to the stock bottles of the higher grade chemicals. When 

 an amount is issued in other than the original container the label must 

 contain the name of the chemical, the name of the manufacturer, the grade 

 and the lot number. Metal spatulas are not to be used in handling mer- 

 curic chloride, iodine, silver nitrate, and other corrosive chemicals. 

 When in doubt use glass or porcelain spoons. The weighing papers are to 

 be used only once and all tools immediately washed and placed where they 

 will drain and dry. Any chemical that is spilled is to be cleaned up 

 immediately and put into the proper receptacle. 



The commercial or technical grade is satisfactory for many purposes 

 such as freezing mixtures and cleaning fluids. U.S. P. chemicals have 

 been prepared to meet the standards of the United States Pharmacopoea (qv) 

 and while suitable for medicinal use may contain other impurities harmless 

 for this purpose. The so-called chemically pure (C.P.) grades are more 

 or less pure but as there are no generally accepted standards for these 

 grades, the purity will vary with different lots and samples from differ- 

 ent manufacturers. This grade is useful when the highest purity is not 

 required. 



The purest chemicals commercially obtainable are further purified 

 and are accompanied with an analysis indicating the tolerances or limits 

 of certain impurities contained. The standards are based on those estab- 

 lished by the American Chemical Society or given in Murray, Standards 

 and Tests for Reagent Chemicals , Van Nostrand. No information is avail- 

 able for other impurities not tested for and when the investigator is 

 in doubt it is essential that he make the necessary tests or further 

 purify the chemicals in accordance with his requirements. Since the 



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