474 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tissues of the animals change portions of the carminic acid to purple 

 carminates, giving a double coloration without further treatment. 



Picric acid added to alcoholic carminic acid in extremely small 

 quantities (best in a dilute alcoholic solution, testing the solution on 

 specimens after each addition) makes a double alcoholic colouring 

 fluid (a so-called picro-carmine). The author has been unable thus far 

 to determine the proportion of picric acid required for this solution, 

 having in every case added an excess. All different kinds of carmine 

 solutions can be made from carminic acid with the advantage of having 

 always uniform strength, of being definite mixtures, and of not 

 spoiling as readily as those made directly from cochineal. 



Incompatible reagents with carminic acid are, of course, all alka- 

 line solutions and nearly all metallic salts ; with ammonic carminate, 

 are naturally all acids ; with all carmine solutions, are bromine and 

 chlorine. 



Hoyer's Picro-Carmine, Carmine Solution, and Carmine Powder 

 and Paste.* — Hoyer proposed f an improved picro-carmine made by 

 dissolving his carmine powder in a concentrated solution of neutral 

 picrate of ammonia. P. Francotte points out that picrate of ammonia 

 is a substance which it is not possible to have constantly at hand, and 

 he has therefore modified Hoyer's preparation in the following 

 manner : — Dissolve 1 gr. of carmine in from 5 to 7 c.cm. of concen- 

 trated ammonia, diluted with the same amount of water ; in 50 c.cm. 

 of distilled water dissolve (warm) 1/2 gr. of picric acid ; mix the two 

 solutions and dilute so as to make 100 c.cm. Then add to the liquid 

 thus obtained 1 gr. of chloral hydrate. If any free ammonia remains, 

 gently warm in a water-bath to drive away the excess, or allow the 

 alkali to volatilize by exposing the liqui(^ to the open air. This 

 solution lasts a long time without changing. 



M. Francotte also supplements Prof. Hoyer's description of his 

 process for obtaining carmine solution. | The latter directs chloral 

 hydrate to be added to the neutral liquid to keep it, but does not state 

 the quantity to be used. M. Francotte forms a carmine solution of 

 10 c.cm. by the addition of distilled water, to which is added 1 gr. of 

 chloral hydrate. 



If a paste is required instead of a powder, Prof. Hoyer directs it 

 to be made with alcohol, glycerine, and chloral, but does not give the 

 quantities. M. Francotte uses to 1 gr. of carmine, 2 c.cm. of alcohol, 

 2 c.cm. of glycerine, and 1 gr. of chloral. 



Dry Injection-masses. — Prof. H. Fol writes that the red gelatine 

 vermicelli mentioned at p. 312 (carmine emulsions) should be pressed 

 out into slightly acidulated water (1 part acetic acid to 1000 parts 

 water). The carmine will otherwise be washed out. 



Imbedding^ Diatoms.§— E. Hitchcock suggests a plan for imbed- 

 ding diatoms from fresh gatherings. It is to prepare an artificial 



* Bull. Soc. Belg. Micr., x. (1884) pp. 75-7. 



t See this Journal, iii. (1883) p. 142. 



J Ibid., p. 141. 



§ Amer. Mon. Micr. Jouru., v. (1884) pp. 54-5. 



