FOI/S CARMINE-GELATIN MASS. 265 



a couple of hours, until thoroughly soft, in a small quantity 

 of water. The water is then poured off and the gelatin melted 

 over a water-bath, and one litre of concentrated solution of 

 carmine in ammonia is poured in with continual stirring. 

 (The carmine solution is prepared by diluting strong solution 

 of ammonia with three or four parts of water and adding 

 carmine to saturation ; the undissolved excess of carmine is~ 

 removed by filtration just before the solution is added to the 

 gelatin.) 



To the mixture of gelatin and carmine, which should have 

 a strong smell of ammonia, sufficient acetic acid is added to 

 turn the dark purple colour of the mixture into the well-known 

 blood-red hue. Exact neutralisation is not necessary. The 

 mass is set aside until it has become firm, and is then cut up 

 into pieces, which are tied up in a piece of tulle or fine netting. 

 By means of energetic compression with the hand under 

 water (it must be acidulated water, 0*1 per cent, acetic acid, 

 otherwise the carmine will wash out : cf. Journ. Roy. Mic. Soc., 

 iv, part 3, 1884, p. 474) the mass is driven out through the 

 meshes of the stuff in the shape of fine strings, which are 

 washed for several hours in a sieve placed in running water in 

 order to free them from any excess of acid or ammonia. The 

 strings are then again melted, and the molten mass is poured 

 on to large sheets of parchment paper soaked with paraffin, 

 and the sheets are hung up to dry in an airy place. When 

 dry the gelatin can easily be separated from the sheets, and 

 may be cut into long strips with scissors and put away, pro- 

 tected from dust and damp, until wanted for use. In order 

 to get the mass ready for use, all that is necessary is to soak 

 the strips for a few minutes in water and melt them over a 

 water-bath. 



The process may be simplified, without giving very greatly 

 inferior results, as follows (Lehrb., p. 13). Gelatin in sheets 

 is macerated for two days in the above-described carmine 

 solution, then rinsed and put for a few hours into water acidu- 

 lated with acetic acid. It is then washed on a sieve for several 



articles used in photography, or direct from Simeon's Gelatin-fabrik, 

 Winterthur, Switzerland. Two sorts, a hard and a soft, are sold ; the softer 

 is to be preferred on account of its lower point of fusion. Probably the 

 photographic gelatins of Hinrichs, of Frankfurt, and of Coignet, of Paris, 

 would answer equally well ; as also the best English preparations. 



