Soni broke the world record for the second time in 24 hours to win the women's 200 metres breaststroke gold at the London Olympics.
The American surged clear of her rivals after trailling after the first lap then taking the lead at the halfway stage to win in a time of two minutes, 19.59 seconds, slashing 0.41 off the previous record of 2:20.00 she set in Wednesday's semi-finals.
Japan's Satomi Suzuki won the silver medal and the bronze went to Iuliia Efimova of Russia.
Soni also won the four-lap event in Beijing four years ago and by winning in London she became the first woman to successfully defend a breaststroke title at the Olympics.
Kromowidjojo of the Netherlands won the gold medal in the women's 100 metres freestyle at the London Olympics on Thursday.
After completing the first lap in fourth place, the flying Dutchwoman hit the accelerator on the last length, surging clear to win in 53.00 seconds.
Aliaksandra Herasimenia of Belarus, who was joint world champion last year, took the silver in 53.38 while China's Tang Yi won the bronze in 53.44.
American teenager Missy Franklin finished out of the medals in fifth place.
Kromowidjojo became the first Dutchwoman to win the classic women's sprint at the Olympics since Inge de Bruijn in 2000.
American teenager Missy Franklin stayed on course to add to her golden haul when she cruised into the final of the women's 200 metres backstroke.
The 17-year-old from Colorado has already won two gold medals in the pool and has a great chance of winning two more before the swimming competition ends on Saturday.
The 200 backstroke is her strongest event after she won it at last year's world championship and she was untroubled winning her semi-final in a time of two minutes, 06.84 seconds.
"I'm really happy with both my splits, my backstroke felt really good tonight, it felt awesome," said Franklin.
"I have a lot of confidence going into it, it's my favourite race and I have so much fun with it, that's the most important part."
With Franklin conserving her energy for the 100 freestyle final, held less than an hour after the backstroke semis, her team mate American Elizabeth Beisel topped the timesheets after winning her semi in 2:06.18.
Zimbabwe's Kirsty Coventry, who won the gold at the last two Olympics and is the current world record holder, qualified sixth but conceded her chances of winning were slim.
"I don't really have any expectations," she said.
"I am just happy to be in the final. The girls who are ahead of me right now are really great, so it's going to be a tight, exciting race."