PURPURIN. 101 



of a similar solution of alum. Extract of logwood added to the 

 until it no longer dissolves freely. Allow the solution to stand for a few 

 days, decant, and to every hundred parts add eighty parts of 1 per cent. 

 acetic acid. Let stand a day and filter. 



187. Cuccati's Iodine Haematoxylin (Zeit. f. wiss. Mik., v, i, 

 1888, p. 55). Dissolve 25 grammes of chemically pure potassic 

 iodide in 25 c.c. of distilled water. Pour this solution gradu- 

 ally and with constant agitation into 75 c.c. of absolute alcohol 

 contained in a stoppered bottle. Close the bottle thoroughly. 

 Rub up in a mortar 75 eg. of crystallised haematoxylin with 

 6 grammes of chemically pure rochealum,* and add 3 c.c. of the 

 iodine solution. Keep the mixture agitated, and add gradu- 

 ally the rest of the iodine solution, then replace the whole in 

 a well-stoppered bottle. Agitate for some time, in order to 

 get the alum to dissolve, and let stand for ten to fifteen hours. 

 Then shake well and filter, taking the usual precautions 

 against evaporation of the alcohol, and preserve in a well- 

 stoppered bottle. 



Objects should be left in the liquid for ten hours, then 

 well washed in water, and mounted in glycerin or washed in 

 alcohol and mounted in balsam. 



The solution is stated to be perfectly stable, and to give a 

 pure chromatin stain, and to be well adapted for staining in 

 the mass, as it never over-stains. 



Other Organic Stains. 



188. Alizarin, so far as I am aware, is only used for Nerve Centres. 

 See Part II. 



189. Purpurin is useful for cartilage and muscle. It is solu- 

 ble in a boiling aqueous solution of alum, from which it normally 

 precipitates on cooling, but may be prevented from so doing by 

 the addition of a certain proportion of alcohol. The employ- 

 ment of an alum solution as a vehicle for the colouring matter 

 has the advantage, at least so far as cartilage is concerned, of 

 fixing the cellular elements at the same time that they are 



* Roche alum, or Roman alum (allume di rocca, alun de roche, alumen 

 rubrum verum, and other synonyms), is an alum originally imported from 

 Civita Vecchia, and much esteemed by dyers from being nearly free from 

 iron-alum. That now sold for it in England is ordinary alum coloured with 

 Venetian red, Armenian bole, or rose-pink (alumen rubrum spurium). See 

 COOLEY'S Cyclopaedia of Pract. Receipts, s. v. " Alum, Romaa." 



