PROFESSOR LETTS ON PHOSPHORUS-BETAINES. 299 
an active couple, and only practice can insure success. The slightest overheat- 
ing causes the metals to agglomerate into a solid semi-fused mass, which is 
quite inactive. 
The iodide of ethyl was prepared by the usual process, washed thoroughly 
with water, distilled, dried with phosphoric anhydride, and rectified. 
The apparatus employed in the preparation of the zinc-ethyl is shown in 
Plate XVIII. figs. 1 and 2. The iodide of ethyl having been added to the 
couple placed in the flask A, the latter is heated in a water bath B until the 
action is at an end (ée., until the iodide of ethyl ceases to distil). The 
condenser C is then shifted from the position shown in fig. 1 to the position 
shown in fig. 2, and is connected with the balloon D which contains dry ether, 
and is provided with two tubes and a tap funnel.* The flask A containing the 
ethyl-iodide of zinc is transferred to a bath of melted paraffin B (fig. 2). A 
stream of carbonic acid is passed through the apparatus, and the paraffin 
heated so long as zinc ethyl distils. 
To arrive at the weight of the zinc ethyl produced, the flask containing the 
dry ether (its two tubes stopped with indiarubber and glass rods) is weighed 
before and after the distillation of the zinc ethyl. This flask is then connected 
with the condenser, which in its turn is connected by a cork and bent tube with 
a large tap funnel E (fig. 3), the cork in the tap funnel being provided with a 
small exit tube. A stream of carbonic acid is then passed through the ap- 
paratus, and when the latter is filled with it, the current is stopped by a pinch- 
cock G. The calculated weight of terchloride of phosphorus is now placed in 
the tap funnel F, and the flask D is placed in a water bath, through which a 
stream of cold water is circulating. The tap of the funnel is then opened, and 
the terchloride run in very slowly. The action is violent—the ether boils (in 
spite of the cold water surrounding the flask), and flows over into the tap 
funnel E, When all the terchloride has been added, the water bath is heated, 
and the remainder of the ether distilled off. The tap of the funnel E is now 
opened, and the ether run off. The tap is then closed, and water slowly added 
through F. This usually occasions a violent action, so that it is advisable to 
add the water slowly at first. A large excess of a strong caustic soda solution 
is now added through F, and a layer of the phosphine rises to the surface, a 
white powder (oxychloride of zinc ?) separating also in large quantity. 
The carbonic acid apparatus is disconnected, the water bath removed, and 
a strong current of steam blown through the tube H (fig. 4), which is pushed 
further through the cork, so that its end is almost at the bottom of the flask. 
The phosphine distils over, and forms an oily layer floating on the water, 
which has passed over with it. When no more oily drops distil, the water is 
* The iodide of ethyl ought to be perfectly dry, otherwise a great deal of gas is evolved by its action 
on the couple. The author has found phosphoric anhydride to be the only reliable dehydrating agent. 
