"Spirit of hartshorn, also simply hartshorn: the aqueous solution of ammomnia (whether obtained from harts' horns or otherwise). salt of hartshorn: carbonate of ammonia; smelling salts" (OED). A hart is another term for stag or deer.

Smelling salts are "a preparation of carbonate of ammonia and scent for smelling, used as a restorative in cases of faintness or headache" (OED).

According to the OED, rubber refers to "A set of games (usually three or five), the last of which is played to decide between the opponents when each has won an equal number; (hence) the winning of more than half the individual games by one side" (OED).

This phrase altogether indicates that Lady Middleton was partaking in a card game upon hearing the news of Marianne.

"Want of adaptation to some purpose, or to the circumstances of the case; unfitness, unsuitableness; incapacity, inability." (OED).

"To deceive by lying, or to tell a lie" (OED).

Example of how gossip plays a big role in society. Gossip is how information goes around and status can go up and down.

This was also custom and simple manners when attending a party. It is offensive if this action was dismissed. It is a way of introducing oneself to the host/hostess and showing gratitude for the invitation.

During this time, the purpose of this was just so that your presence was known and acknowledged. This is custom.