A YEAR IN SCIENCE 55 



minutes. Treat each separately with one of the 

 following : 



1. Dilute sulphuric acid. 



2. Dilute sulphuric acid, then wash and neutralize 

 with weak ammonium hydroxide. 



3. Dilute acetic acid; wash, etc., as in 2. 



4. Oxalic acid, dissolved in hot water; wash, etc. 



5. Acid potassium oxalate, dissolved in hot water ; 

 wash, etc. 



Which is the most rapid and effective in action? 

 Examine specimens number one and number two after 

 several days have elapsed. Has the acid attacked the 

 cotton as well as dissolved the stain? Why should the 

 cloth always be thoroughly washed after treatment? 

 What is the added advantage of using ammonia water ? 



Exercise 31. Oxygen. 



Object: To determine some of the properties of 

 oxygen. 



Apparatus 



Potassium chlorate Bunsen burner 



Manganese dioxide Large mouth bottles 



Florence flask Glass plates 



Rubber stopper (one-hole) Deflagrating spoon 



Pneumatic trough Charcoal 



Delivery tube Sulphur 



Ring stand Pine splinter 



Wire gauze Lime water 



Directions: Place in the flask a mixture of four 

 parts of potassium chlorate and one part of manganese 

 dioxide. Insert into the mouth of the flask the rubber 



