Among matters not ordinarily assumed to be within the scope of the power of a partner are the following: Confessions of judgment; submission to arbitration; the making of a general assignment;7 the sale of the business or its necessary equipments; the conveyance or mortgage of realty; the making of the firm partner with another person or firm; using the firm name as a gratuitous favor in accommodation or guaranty; the making of any contract or covenant under seal, if the seal is necessary or usual and not merely superfluous;8 the making of any illegal or usurious contract.