what are the symptoms of chemical poisoning in dogs?

My 2 dogs became very ill and died almost simultaneously. I believe they may have ingested something toxic that the neighbour threw in my yard. One dog became extremely weak, had a blood transfusion but did not improve as her liver gave out. Her skin turned very yellow and she was unable to move herself. The other dog started bleeding profusely , became extremely weak and had to be put down.

Somebody must have been real sick of listening to those things bark! That sounds like two completely different poisons – if they were poisons.