Four prototype HALTT (" helicopter Alert and Threat Termination ") sensors are now on board Black Hawk helicopters and deployed to Afghanistan, as Danger Room alum Nathan Hodge reports.
四件HALTT(直升机预警与威胁解除)传感器样件目前已装在黑鹰直升机上，应用于阿富汗，如险情办公室Nathan Hodge所报道的。
In potash it turns black, but in alum nothing happens until you bring it to the boil, then purple colour comes flooding out.
在碳酸钾中，它变成黑色，而在明矾中一开始却什么反应都没有，直到煮沸后紫色都溢出来了。
In potash it turns black, but in alum nothing happens until you bring it to the boil, then purple colour comes flooding out.
在碳酸钾中，它变成黑色，而在明矾中一开始却什么反应都没有，直到煮沸后紫色都溢出来了。
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