CHAPTER XXL 235 



The mass, having been perfectly neutralised, is strained through 

 new flannel. 



480. How to Neutralise a Carmine Mass (VILLE, Gaz. hebd. d. Sci. 

 med. de. Montpellier, Fev., 1882 ; may be had separately from 

 Delahaye et Lecrosnier, Paris). VILLE points out that when 

 carmine is treated with ammonia a certain proportion of the ammonia 

 combines with the carmine and the rest remains in excess. It is 

 this excess that it is required to neutralise precisely, not the whole of 

 the ammonia employed. 



To neutralise the acidity of commercial gelatin, it should be 

 washed for an hour or so in running water. 



As to the neutralisation of the colouring mass, VILLE is of opinion 

 that the sour smell cannot be safely relied on in practice, and 

 prefers to employ dichroic litmus paper (litmus paper sensitised 

 so as to be capable of being used equally for the demonstration of 

 acids and bases). For directions for preparing this see loc. cit. or 

 previous editions. 



481. HOYER'S Carmine-Gelatin Mass (BioL Centralb., 1882, 

 p. 21). Take a concentrated gelatin solution and add to it the 

 needful quantity of neutral carmine staining solution (loc. cit., p. 17). 

 Digest in a water-bath until the dark violet-red colour begins to 

 pass into a bright red tint. Then add 5 to 10 per cent, by volume 

 of glycerin, and at least 2 per cent, by weight of chloral, in a con- 

 centrated solution, and strain. 



482. FOL'S Carmine-Gelatin Mass (Lehrb., p. 13). This can be 

 kept in the dry state for an indefinite length of time. 



Gelatin in sheets is cut into strips which are macerated for two 

 days in carmine solution (prepared by diluting one volume of strong 

 ammonia with three of water and adding carmine to saturation, 

 and filtering after a day or two). The strips are then rinsed and 

 put for a few hours into water acidulated with acetic acid, then 

 washed on a sieve for several hours in running water, dried on parch- 

 ment paper, or on a net, and preserved for future use. To get 

 the mass ready for use, the strips are soaked for an hour in water 

 and melted on a water-bath in 10 to 20 parts of water. 



For another process, which is said to give somewhat better results, 

 but is more complicated, see loc. cit., or Zeit. wiss. Zool., xxxviii, p. 492, 

 or previous editions. 



483. KRAUSE'S Carmine-Gelatin Mass (Zeit. wiss. Mik., xxvi, 1909, 

 p. 1). 100 grms. gelatin soaked in water, put for two to three days into 

 a solution of 15 grms. carmine in 2 litres of water with 100 grms. of borax, 



