12 



point is reached, — which is ahowQ by the swelling and breaking- 

 up of the scum, — the heat should be stopped and the juice left 

 quiet for about five minutes. The scum will then be quite hard^ 

 and may be easily removed from the surface of the clear liquid. 

 Much will depend on a good defecation. If the defecation has- 

 been properly conducted, the liquid will be clear, free from par- 

 ticles, and of a pale yellow color. If the S3ura is of a light color 

 and thin, while the liquid below is opaque and has a greenish 

 color, it shows that too little lime has been added ; while if the 

 juice is very dark, too much lime has been used. Much nicety of 

 judgment is required to make a good defecation, which can only 

 be obtained by experience. 



USE OF SULPHUROUS ACID. 



The clear juice from the defecator is now tolerably pure, most 

 of the impurities having been eliminated. It contains, however, 

 considerable lime, which if allowed t3 remain will give us a dark 

 syrup, and if present in sufficient quantities will impart a more or 

 less bitter taste to the syrup. To avoid this we must neutralize 

 the lime, just as before we neutralized the acid. For this purpose 

 sulphurous acid is much used. This acid may be added to the 

 juice in the defecator after removing the scum, or it may be added 

 to the juice in the evaporating pan. A sufficient quantity should 

 be added to give to the juice a distinct acid reaction, or until a 

 slip of blue litmus paper, dipped into the juice, is reddened. To 

 accomplish the same result, many preparations have been sold to 

 the farmers and other syrup manufacturers by agents and peddlers. 

 I would here advise every one to leave all such preparations alone. 

 Most of them are either harmful or good for nothing, while others 

 are but modifications of the methods which I have des3ribed and 

 for which the buyer pays an exorbitant price. As long as I 

 remain at the university inquiries as to any method will be an- 

 swered. Before closing this report we will de33ribe methods by 

 which sulphurous acid may be made at syrup works. 

 BOILING TO SYRUP. 



The juice should be boiled down as rapidly as possible, the 

 scum which comes to the surface being skimmed off. If con- 



