Huck's interview with Mrs. Loftus comes in Chapter 11 of the novel, and is notable for a number of different reasons. However, most of all, and relating to your question, it is very revealing about the attitudes that it reveals about slavery. Mrs. Loftus is like other characters in the novel, such as Aunt Sally, who on the one hand are presented as very kind and generous people, but who on the other maintain racist views that contradict the generosity of their characters. Note how when Mrs. Loftus is talking to Huck about his and Jim's disappearance, she states how her husband is going to hunt Jim down:
"Does three hunded dollars lay around every day for people to pick up? ... I didn't say any more, but I done some thinking. I was prettynear certain I'd seen smoke over there, about th head of the island, a day or two before that, so I says to myself, like as not that nigger's hiding over there; anyway, says I, it's worth the trouble to give the place a hunt."
The plan to send her husband at night to surpise Jim and "hunt up his camp fire all the better for the dark" demonstrates this aspect of the character of Mrs. Loftus. She is presented as a kind and generous woman in her attitude towards Huck, however the way she talks of hunting Jim down as if he were some sort of animal shows a darker side to her character. Twain seems to be suggesting that within all of us lies an equal capacity for goodness and for questionable deeds.