They are used to shoot tungsten film in daylight. There are actually several #85 for slightly different balance.

#85 (KR 12)
Light balancing filter. Type A tungsten (artificial light) color films can be used in daylight or with an electronic flash. The filter is brown and eliminates the overall blue cast. The filter factor is approximately 2.
#85B (KR 15)
Light balancing filter. Type B tungsten (artificial light) color films can be used in conditions such as mountains where even daylight film would require a KR 3 or a #6 filter.
The filter factor is approximately 2.3.
#85C
Amber. Converts 5500K (daylight) to 3800K lighting.
From http://www.jackspcs.com/filters.htm

You would have to experiment, but it might work about like an orange for black and white -- dunno, never tried it.

DaveT