and Laboratory Methods. '^405 



tinuous heating or by decreasing the amount of linseed oil, and softer by increasing 

 the proportion of linseed oil. 



As in preparation (A) so in preparation (B), a more thorough mixture is 

 obtained if the coal tar and resin are first well mixed and then the paraffin added, 

 than if all the ingredients are at once added together. This preparation requires 

 more heating and stirring than preparation (A) in order to cause the ingredients 

 to mix ; and at best there will be only a partial mixture. Coal tar and resin 

 being heavier than paraffin tend to collect at the bottom, so that in this prepara- 

 tion it was found best to weigh out the desired amount of substances used, in 

 proper proportion for each pan separately, and melt and mix them in each pan. 



As above stated, neither of these preparations is ideal ; both lack some essen- 

 tial characteristics. Preparation (A), while insoluble in water and formal, is 

 slightly soluble in 60 per cent, alcohol, and quite readily soluble in strong solu- 

 tions, and consequently is not satisfactory for dissection in solutions of alcohol 

 stronger than about 50 per cent. 



Preparation (B) is practically insoluble in 96 per cent, alcohol as well as in 

 formal and water, and is consequently satisfactory for dissection in these solu- 

 tions ; but this preparation does not adhere to the pans as tenaciously as prepa- 

 tion (A), and it might also be improved by being made slightly darker in color. 



Cost. — Coal tar and resin are usuall}'^ sold by dealers in plumbing material, 

 the former at 25c. per gallon, and the latter at 5c. per pound. Linseed oil 

 is handled by dealers in paint. It is retailed at from 40c. to 80c. per gallon. 

 Paraffin may be obtained from druggists or dealers in laboratory supplies, at 

 about 'iOc. per pound. 



According to the above prices the approximate cost of the preparations would 

 be as follows : 



Preparation (A). 



1 lb. Linseed oil, - - - - $ .OS 



2 lbs. Coal tar, . - . - .08 



8 " Resin, .40 



2 " Paraffin, . . . . .40 



Total, 13 lbs. ----- $ .96 

 Cost per pound, 7fc. 



Preparation (B). 



2 lbs. Coal tar, ----- $ .08 



4 " Resin, .20 



10 " Paraffin, ----- 2.00 



Total, 16 lbs. $2.28 



Cost per pound, 14 ^/(c. 

 The amount of either of the preparations required to cover the bottom of a 

 dissecting pan 5x8 inches, about |^ inch deep, weighs approximately one-half 

 pound, making the cost of preparation (A) per pan about 4 c, and of preparation 

 (B) about 7 c. S. O. Mast. 



Hope College. 



