FREE BOOKS

Author's List




PREV.   NEXT  
|<   13   14   15   16   17   18   19   20   21   22   23   24   25   26   27   28   29   30   31   32   33   34   35   36   37  
38   39   40   41   42   43   44   45   46   47   48   49   50   51   52   53   54   55   56   57   58   59   60   61   62   >>   >|  
detection is a matter of considerable difficulty. Huebl says (_Dingl. Jour._, p. 338) that the most reliable method of estimating the adulteration of beeswax is that proposed by Becker, and known as the saponification method. The quantity of potassic hydrate required to saponify one gramme or 15 grains of pure beeswax varies from 97 to 107 milligrammes. Other kinds of wax and its substitutes require in some cases more and in others less of the alkali. This method would, however, lead to very erroneous conclusions if applied to a mixture of which some of the constituents have higher saponification numbers than beeswax and others higher, as one error would balance the other. To avoid this, the quantity of alkali required to saponify the myricine is first ascertained, and then that required to saturate the free cerotic acid. In this way two numbers are obtained; and in an investigation of twenty samples of Austrian yellow beeswax, the author found these numbers stood to each other almost in the constant ratio of 1 to 3.70. Although this ratio cannot be considered as definitely established by so few experiments, it may serve as a guide in judging of the purity of beeswax. The experiment is carried out as follows: 3 or 4 grammes of the wax that has been melted in water are put in 20 c.c. of neutral 95 per cent, alcohol, and warmed until the wax melts, when phenolphthaleine is added, and enough of an alcoholic solution of potash run in from a burette until on shaking it retains a faint but permanent red color. The burette used by the author is divided in 0.05 c.c. After adding 20 c.c. more of a half normal potash solution, it is heated on a water bath for 3/4 hour. Then the uncombined excess of alkali is titrated with half normal hydrochloric acid. The alcohol must be tested as to its reaction before using it, and carefully neutralized with the acid of phenolphthalein. To saturate the free acid in 1 gramme of wax requires 19 to 21 milligrammes of potassic hydrate, while 73 to 76 milligrammes more are necessary to saponify the myricine ether. The lower numbers in the one usually occur with low numbers for the other, so that the proportions remain 1 to 3.6 or 1 to 3.8. For comparison he gives the following numbers obtained with one gramme of the more common adulterants: ----------------+----------+----------+---------+--------+ | To | To | Total | | |ne
PREV.   NEXT  
|<   13   14   15   16   17   18   19   20   21   22   23   24   25   26   27   28   29   30   31   32   33   34   35   36   37  
38   39   40   41   42   43   44   45   46   47   48   49   50   51   52   53   54   55   56   57   58   59   60   61   62   >>   >|  



Top keywords:

numbers

 

beeswax

 

alkali

 

saponify

 

required

 

method

 

gramme

 

milligrammes

 

potash

 
burette

obtained
 
normal
 

myricine

 
saturate
 

higher

 
author
 
solution
 

saponification

 

quantity

 

potassic


alcohol

 

hydrate

 
melted
 
divided
 

warmed

 

neutral

 

alcoholic

 

phenolphthaleine

 

shaking

 

permanent


retains

 

hydrochloric

 

proportions

 

remain

 

common

 

adulterants

 

comparison

 
uncombined
 

excess

 

titrated


adding

 

heated

 
neutralized
 

phenolphthalein

 

requires

 

carefully

 
tested
 
reaction
 

constant

 
require