356 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 3 



and plant life is accomplished, but the gases and salts are not de- 

 stroyed, reports Nogier (1910) among other authors. 



In recent years the method of sterilization of water by ultraviolet 

 irradiation has not been very widely used, owing to the competition 

 of cheaper and somewhat simpler chemical processes such as 

 chlorination for drinking water and coppering for swimming pools. 

 There are, however, fields of usefulness in smaller-scale operations 

 where the chemical processes are objectionable, especially where in- 

 jury might be caused by an overdose, and in these the ultraviolet 

 method is preferable. Some of these smaller-scale operations are 

 the preparation of water for surgical purposes ; sterilization of water 

 for bottling, or for the supply of small consumers, such as individual 

 homes; sterilization of water for washing butter, for the margarine 

 industry, and wherever the water is to be incorporated in food ; and 

 the sterilization of water on shipboard, especially on ships navigat- 

 ing inland waters (Ellis and Wells, 1925). 



Wine and cider can also be quickly sterilized by ultraviolet irra- 

 diation and, according to Maurain and Warcollier (1910), the wine 

 has the greater transparency for the ultraviolet rays. Before the 

 war, according to Henri, Helbronner, and von Recklinghausen 

 (1915), the method of " ageing " wine by means of ultraviolet irrad- 

 iation was utilized to a great extent in France. The ultraviolet 

 changed the taste and color of the wine, and in a few minutes the 

 new wine had assumed the characteristics of old wine. 



The sterilization of milk is difficult because its flavor and food 

 value must not be injured in any way during the process. These 

 properties have always been injured in a small way no matter what 

 means of sterilization is employed, and ultraviolet has not proved 

 to be an exception. Ultraviolet rays are desirable for milk steriliza- 

 tion because when the milk is incompletely sterilized by irradiation, 

 the noxious bacteria are more affected than the relatively desirable 

 members of the lactic acid group. Helbronner and von Reckling- 

 hausen (1915) have found that complete sterilization by ultraviolet 

 alone is difficult and that the necessary prolonged treatment has 

 deleterious effects upon the flavor and digestive qualities of the 

 liquid. For this reason, they have proposed the use of a combination 

 of heat sterilization together with ultraviolet rays. When milk is 

 given a short heat treatment at a temperature of about 60° C. the 

 bacteria in it become so weakened that ultraviolet rays destroy them 

 very readily. It is claimed that by this combination treatment the 

 milk is not heated sufficiently to alter the flavor and that a very short 

 irradiation time completely sterilizes the milk. 



Monvoisin, Barret, and Robin (1914) have a patent on the use 

 of ultraviolet irradiation for the process of sterilizing the surface 



