Microscale glassware kits include connectors to fit the smaller glassware. The black connectors should be used when are present. Otherwise, the tan connectors can be used. The connectors can combine different pieces of glassware or components

high boiling aromatics

with the same ground glass joint.

Explanation:

The black connectors are more resistant to the reactant than the white connectors. This implies that the black connectors should be used when high boiling aromatics are present, Else, the tan connections can be used.

Thus, the connectors can combine different pieces of glassware or components with the same ground glass joint.

it is called acid bonding