REGULATION OF SALE 193 



white. The "uaiac tincture should not be used perfectly fresh but 

 should have stood a few days and its potency have been determined. 

 Aceordins' to the observations by Glage, the guaiac-wood tincture 

 appears to be more reliable than the harz tincture. Zink recommends 

 the addition of a few drops of weak solution of hydrogen dioxide, 

 as this causes the reaction to be much surer and sharper. 



Of the fwii methods, the guaiac method Ls preferable in that the 

 tincture is very lasting and may be kept a year without becoming 

 ineffective, while the paraphenylendiamin solution must be renewed 

 quite often ; on the other hand, the guaiac method is, perhaps, hardly 

 so accurate as the Storch method. 



Other substances are useful as reagents in combination with 

 liydrogen din.xide, as solution of potassium iodide with starch 

 (Storch, du Rni, Kohler and others) and ursol (Utz) ; besides tliesc, 

 a methylene-blue-formalin solution (Schardin.ner) has been suggested 

 for this purpose. 



[ Storch 's test may also be used for the purpose of 

 detecting the adulteration of fresh milk with diluted 

 condensed milk. In this case it is well to make the test 

 comparative by running a parallel sami)le of milk known 

 not to have been heated. L. P.] 



The sale of milk prcpdratioits which are made eitlier 

 by using foreign additions or by some special manipula- 

 tion of the milk should be permitted only when the milk 

 has been produced under the requirements above stated 

 and only on declaration of the composition of the prep- 

 aration. 



.1//7/,- cdiifdiucr.'^. In case the milk is retailed in 

 containers, there should be some stipulation in 

 regard to these. ]\[etal cans should be of tinned iron; 

 for tinning, no tin should be used that has more lead 

 than is absolutely necessary; the form must be such 

 that they can be easily cleaned. Bottles are to be made 

 of clear glass so that every impurity is noticeable; 

 their form nmst, likewise, make satisfactory cleansing 

 ])ossihle. 



In recent years, the large milk companies have en- 



13 



