FIXATIVE MIXTURES 



H5 



formaldehyde 

 picric acid . 

 acetic acid (glacial) 

 water . 



10 g 



1*05 g 

 5 nil 

 90 g 



If each of these figures be increased by one-ninth, we have the 

 composition expressed as percentages of the weight of w^ater: — 



formaldehyde . . . . , 11 g 



picric acid . . . . . . i-2 g 



acetic acid (glacial) .... 5-6 ml. 



The concentrations of the solutes are therefore: — formaldehyde, 

 11% w/W; picric acid, i-2%, w/W; acetic acid, 5-6% v/W. These 

 are the figures given in table 8. 



Care has been taken to make the table as accurate as possible, 

 but perfect accuracy cannot be achieved. Some inventors of 

 fixative mixtures give amounts in drops. It is impossible to be sure 

 how much HXO3 there w^as in Perenyi's Saltpetersdure 10%. 

 Saturated solutions are of varying concentrations. Authors do not 

 tell us how much (if any) water of crystallization they introduce 



TABLE 9 



Analysis of 2$ aqueous fixative mixtures: summary of part of the 

 information contained in table 8. 



with sodium sulphate. The attempt has been made to get the 

 concentrations correct, where possible, to two significant figures. 

 There w^ould be no point in trying to go beyond this. 



The table will enable the reader to make a direct comparison of 

 any particular fixative mixture in the list with any other. Certain 



K 



