294 



FOOD AND FOOD ADULTERANTS. 



ture gradually raised until it reaches 80 C., beyond which it should 

 not be carried. By holding it at this temperature for about half an hour 

 and taking the bottle out of the can and shaking it occasionally all the 

 CO 2 may be driven off. Then the tube from a suction pump is con 

 nected with a calcium chloride tube and this in turn with the soda lime 

 tube. The valve of the tap is then closed, the latter removed from the 

 bottle, connected with a soda lime tube, and by gradully opening the 

 valve, a stream of air, from which the CO 2 has. been removed, is drawn 

 through the apparatus by the pump, so that all the CO 2 contained in it 

 is drawn into the soda lime tube and absorbed ; the increase in the 

 weight of the latter, of course, gives the weight of CO 2 in the beer. The 

 quantity of the beer is measured or -weighed, that which has been car- 

 ried into the Erleuineyer flask being added, and the per cent, ascer- 

 tained. 



In the case of large bottles it may be found necessary to add a second 

 soda lime tube, and it is best to use fresh soda lime for each determina- 

 tion. It was found necessary to modify the champagne taps, as the 

 thread with which they are provided cuts the cork too much and allows 

 the escape of the gas. Accordingly this thread was turned off entirely, 

 leaving a smooth tube, as shown in the figure. 



FIG. 15. 



This can be forced through the cork with little difficulty, and allows 

 110 leakage of gas. It was also found necessary to have the cocks re 

 ground to make them fit accurately. 



The patent rubber-stopper beer bottles presented a difficulty to this 

 method of anaysis, as it was impossible to make a gas-tight connect ion 

 with them without the escape of the confined gas. In these the gas 

 was estimated by loss of weight, calcium chloride and sulphuric :icid 

 tubes and connections being weighed with the bottle on a large bal- 

 aucc, the bottle opened and connection made as quickly as possible, 1 he 

 gas driven off as before, and the loss ascertained by weighing the en- 

 tire apparatus again. It is necessary to raise the heat very gradually 

 to prevent the filling up of the tubes with the beer carried over by the 

 bubbles. There is a slight error from the watery vapor which escapes 

 with the, pressure, of gas when the bottle is opened, and altogether tin- 

 determination is not so satisfactory as with the cork stoppered bottles. 



