Question

why is acid poured into burette, not alkaline during titration ​

Answer 1

Answer:

because the stopcock might “freeze up.” With borosilicate glass and Teflon stopcock plugs, the problem hardly exists anymore.

Answer 2

Answer:

When it was necessary to use the alkali in the burette a ruber pinchcock was used instead of a stopcock because the stopcock might "freeze up". With borosilicate glass and Teflon stopcock plugs, the problem hardly exists anymore.