514 MARINE PRODUCTS OF COMMERCE 



Calculations Involved in Vitamin A Determination 



Sanford (1948) has developed a method for the rapid determination of vitamin 

 A in fish hvers: 



"In nearly all transactions involving fish livers the livers are sold on the basis of the 

 number of millions of units of vitamin A per pound of liver. This figure is calculated 

 from the data obtained from the oil and vitamin A analysis. A discussion of the method 

 of making this calculation follows: 



"The oil content of the livers is reported as a percentage based upon weight. For 

 example, one lot of soupfin shark livers analyzed 62.3 per cent oil. This meant that, on 

 the average, 62.3 pounds of oil were contained in every hundred pounds of this par- 

 ticular group of soupfin shark livers. 



"Vitamin A potency of liver oil is reported as the number of units of vitamin A con- 

 tained in one g of the oil. In the analysis of the soupfin shark liver just mentioned it was 

 found that 1 g of oil contained 116,300 spec, units of vitamin A. It may seem strange 

 that the potency of the oil is reported in grams when most common materials are weighed 

 in pounds and ounces. However, the chemist has found it convenient to use the metric 

 system in the laboratory, and he naturally reports his results in the units of measure 

 in which he ordinarily works; but, except for making the labor of an additional multipli- 

 cation necessary the reporting of vitamin A on the gram basis causes no particular diffi- 

 culty. 



"Assuming then that the oil content and oil potency have been obtained from a 

 chemical analysis the first step is to calculate the number of units of vitamin A in a 

 pound of the oil. Since there are 454 (or more accurately, 453.6) grams to a pound, this 

 can be done by multiplying the number of units in 1 gram of the oil by 454. As an ex- 

 ample, oil from the soupfin shark just mentioned would have yielded 52,800,200 units per 

 pound as follows: 



"116,300 X 454 = 52,800,200 spec, units of vitamin A per pound. 



"This gives the oil potency or the number of units per pound of oil. Since only a part 

 of the liver is composed of oil, it is necessary to multiply the oil potency by the fractional 

 amount of oil in the liver to get liver potency. To do this it is first necessary to convert 

 per cent into a decimal, which can be done by dividing per cent by 100 as follows: 



62.3 

 62.3 per cent = = 0.623 parts of oil per unit weight of liver. 



"Hence, liver potency is obtained by multiplying oil potency by this figure: 



52,800,200 X 0.623 = 32,894,524.6 spec, units of vitamin A per pound of liver. 

 It is conventional to report liver potency in terms of millions of units per pound. There- 

 fore, the number of units per pound is divided by a million as follows: 



32,894,524.6 ^ . „ r " , r, 



— = 32,894,524.6 million spec, units of vitamin A per pound of liver. 



"This is a cumbersome figure which can be simplified if the factors involved in its 

 determination are considered. That is, if an independent attempt were made to rede- 

 termine the amount of vitamin A in these livers, the experimental error is such that these 

 figures could not be reproduced again exactly. Experience has shown that any figures 

 beyond the first four are meaningless. Therefore, these excess figures can be dropped and 

 the vitamin A potency of the livers reported as 32.89 million units per pound of liver." 



Chemical Control in Oil Production 



Since the success of a vitamin A oil processor depends upon so many variable 

 factors, practically all those engaged in this industry employ a staflF of trained 



