62 MILK HYGIENE 



cylic acid, benzoic acid, potassium bicromate and for- 

 malin. Earely, peroxide of hydrogen and fluorides are 

 used. 



a. Boric acid is sometimes used as such, sometimes 

 as borax, and is able, when added in the proportion of 

 0.1 per cent, to 0.2 per cent., to prevent bacterial growth 

 for several days so that coagulation does not take place. 

 It is said that boric acid is a harmless substance, and it 

 is true that it has been used as medicine in quite large 

 doses without injurious effect being perceived. On the 

 other hand, observations and investigations have been 

 made which fully prove that boric acid maj- cause 

 illness, • vomiting and diarrhoea, and if given for a 

 prolonged time, may injure the kidneys and cause some- 

 what rapid and not inconsiderable loss of weight; the 

 latter depends partly on the fact that the food is not well 

 assimilated and partly on the increase of metabolism 

 (Rubner). Experiments on animals have confirmed the 

 results of these investigations and, indeed, demonstrate 

 that boric acid may even cause a fatal poisoning; for 

 example, Annett fed five kids with milk that was mixed 

 with 1 gr. boric acid to the litre; all five died in the 

 course of 2 to 4 weeks. It may be said, further, that 

 boric acid is excreted from the organism slowly so that 

 the toxifc effect is not temporary and transitory, so boric 

 acid must be considered to be an injurious substance and 

 its addition to milk and other food is to be forbidden. 



Boric acid may be detected in milk in different ways : 



According to Villiers and Faj'olle, milk is evaporated 

 to dryness and ignited, the ash is wet with sulphuric acid, 

 ?> c.c. methyl alcohol is added and the solution is distilled 

 until sulphuric acid vapor begins to appear. The vapor 

 is ignited and if boric acid be present, in even a very 

 small (juantity, this will burn with a green flame. 



Meissl recommends the following method : 100 c.c. of 



