GENERAL DIRECTIONS OF WORK 



FOREWORD 



NEATNESS and order are the first requisites of proper laboratory 

 work of any kind. Neat workers only can be accurate manipula- 

 tors. Orderly work leads to fewer mistakes than work which 

 is done hurriedly and without system or plan. 



In order to obtain proper quantitative results absolute clean- 

 liness is essential. All of the apparatus used should be left in a 

 chemically clean condition. Most of the apparatus can best be 

 cleaned by rinsing well with warm water, then washing with soap 

 and water and brush or cloth, then again rinsing well with warm 

 water, and finally rinsing with distilled water. Never dry beakers 

 or other chemical vessels with a towel. If it is necessary to dry a 

 vessel quickly rinse with alcohol and ether and dry with a current 

 of air or dry by gently warming after rinsing with- distilled water. 

 Use judgment in cleaning your apparatus. Always use the 

 appropriate solvent first, then remove the excess of the solvent 

 and continue the washing as above. Pipettes and burettes after 

 the preliminary cleaning with the appropriate solvent and rinsing 

 as above indicated, often require further treatment with cleaning 

 mixture. Finally rinse well with warm water and distilled water. 

 Do not use cleaning mixture unless it is necessary. 



In measuring reagents do not insert the pipette into the reagent 

 bottle, but pour off about the amount desired into a dry vessel 

 and then measure therefrom by the pipette. Never return solid 

 or liquid reagents to the stock bottles, 



Caution 



Acetone, alcohol, ether, benzine, glacial acetic acid, and 

 toluene are inflammable. Never heat any of them over the free 



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