§ 157. Release of part of mortgaged premises. If the owner of
mortgaged premises sell a part thereof, the comptroller, on application
and with the consent of the mortgagor or such owner may release the part
of the mortgaged premises sold from the lien of the mortgage. Such
release, however, shall not be given unless a sum approved by the
comptroller shall be first paid upon the mortgage and unless the part of
the mortgaged premises remaining unsold, exclusive of buildings and
prior liens, is worth double the residue of the mortgage debt. The
comptroller shall execute such release in the usual form, which, when
acknowledged, shall be recorded by the county clerk and a minute thereof
made upon a margin of the mortgage.