Wales stayed on course for the 6 Nations Grand Slam after doing the hard work early on and then hanging on against a second-half assault to continue their recent stranglehold over Scotland.
Two tries in the first half from Josh Adams and Jonathan Davies were probably short of what the Welsh deserved as they seemed likely to run away with the game, but a couple of missed chances kept Scotland in touch.
The second half was almost one-way traffic with Scotland driving repeatedly into the Welsh 22, but they managed to breach the blanket red defence just once through Darcy Graham.
There was more encouragement for Scotland here than after the desperately disappointing display in Paris, but once again they missed some of their quality injured players and even when they were on top in the second half there was more than a hint of frantic desperation as they tried to fight back.
The first-half errors in the end gave them too much of a mountain to climb, and losing all their back three players to injury did not help matters.
Like Paris, there was a feeling at the break that the Scots were fortunate to be just 15-6 down, with Wales passing up some great chances as well as their two tries in the opening period.
Scotland did begin fairly brightly and a series of phases gradually made ground into the Welsh 22 only to be stalled when skipper Stuart McInally was called for a neckroll at a ruck on a Welsh defender.
But after the Scots won a penalty in their own half and kicked clear, the Welsh were offside in the backline and Russell kicked the home side ahead.
The lead lasted barely three minutes, however, as Wales started to get some go forward with their carrying and moved the ball slickly wide to make space for Josh Adams down the touchline, but the wing went far too easily around Blair Kinghorn’s ineffectual tackle for an easy score, converted by Gareth Ainscombe.
Scotland were forced into a confusing series of changes with Hamish Watson on for a head injury to Jamie Ritchie only for the returning back rower was withdrawn himself for Fraser Brown.
But there was some welcome spark for the home crowd from home debutant Darcy Graham, who dodged through one tackle, shook off another and beat Liam Williams one on one only for Alun Wyn Jones to make a try-saving tackle in the shadow of the Welsh posts.
Scotland looked to ram home the territory made by Graham’s surge but inevitably Wales transgressed and Russell kicked his second penalty.
Again, Wales were quick to get the scoreboard moving again when McInally didn’t roll away from a tackle and Ainscombe stretched his side’s lead to four with the penalty, and then the Welsh really got into their stride.
They put together a powerful and physical series of 30 phases in the Scottish 22 after a scrum penalty won them the position, but they passed up at least one two-man overlap before Jonathan Davies slipped through a stretched Scotland defence for the second score that went unconverted.
With Tommy Seymour and then Blair Kinghorn taken off injured, Wales clearly saw a chance to put the game to bed right away, but Ainscombe hit the post with a penalty, replacement Adam Hastings and Graham just getting over to stop Adams scoring his second try.
Still Wales forced a scrum five from a poor Scottish lineout but a knock-on saved the Scots from any further damage before the break.
Scotland needed to just get some ball to work worth, and although it took them 20 minutes before they made the breakthrough, the tide certainly turned after the break.
Prop Allan Dell made the first salvo with a 50 metre charge but the Scots were a little too frantic trying to make a breakthrough and a Russell pass went astray.
Then a high tackle on Grigg set up the Scots in the 22 but the Scots couldn’t force there way through, a key tackle by replacement Dan Biggar on Hastings stopping the home side’s best chance.
Another high tackle by North on Ali Price gave the Scots position just on the hour mark and this time they made it count, Russell’s inside pass to replacement back Byron McGuigan creating the space and Hastings proving the link to Graham to score in the corner.
Russell missed the conversion, but Scotland had the momentum now and Russell’s clever grubber set up another maul, but this time the Wales disrupted it and the ball was lost.
At the other end a loose pass from Pete Horne went to ground, was snapped up by Adams and the Scots had to scramble to recover and force a knock on.
Watson, back on for Josh Strauss, raised the hopes of the home crowd again with a couple of storming runs but inside the 22 the Welsh defence stiffened and were able to repulse the increasingly desperate attempts of the home side to turn the game.
Instead Price, moved to the wing when Graham was another to be forced off, mis-timed a tackle on Ainscombe and was penalised, allowing Wales to clear.
They set a bridgehead inside the Scots 22, forcing a penalty with the last play which Ainscombe kicked to secure the Welsh victory and set up a Grand Slam chance against Ireland next week.
Att 67,200
Scotland: B Kinghorn; T Seymour, N Grigg, P Horne, D Graham; F Russell, A Price; A Dell, S McInally (capt), WP Nel; G Gilchrist, J Gray; M Bradbury, J Ritchie, J Strauss.
Replacements: F Brown for McInally 70, S Berghan for Nel 65, B Toolis for Gray 65, H Watson for Strauss 65, G Laidlaw for Graham 65, A Hastings for Kinghorn 32, B McGuigan for Seymour 21.
Wales: L Williams; G North, J Davies, H Parkes, J Adams; G Anscombe, G Davies; R Evans, K Owens, T Francis; A Beard, A W Jones (capt); J Navidi, J Tipuric, R Moriarty.
Replacements: E Dee for Owens 65, N Smith for Evans 63, D Lewis for Francis 65, J Ball for Beard 63, A Wainwright for Moriarty 70, A Davies for G Davies 70, D Biggar for Williams 48, O Watkin for Parkes 74.