Abhi Khandelwal
Senior Vice President and Chief Financial Officer at IDEX
Thanks, Eric. Before jumping into the consolidated results on Slide 4, I want to highlight our team's consistent ability to execute, as you've seen in the results, delivering strong profitability and free cash flow in the first quarter despite challenging year-over-year comparables.
Moving on to the consolidated financial results. All comparisons are against the prior year period unless stated otherwise. [Indecipherable] $820 million in the first quarter were down both 1% overall and organically. We experienced an organic decrease in FMT and HST, while FSDP grew low double digits, driven by strength in dispensing and emerging markets. First quarter sales of $801 million were down 5% overall and down 6% organically. We experienced a 13% organic decrease in HST and a 3% organic decrease in FMT, while FSDP grew by 2% organically. First quarter gross margin was 44.6%, declining 60 basis points while adjusted gross margin was 45%, contracting 20 basis points due to our volume leverage, partially offset by price/cost and operational productivity. First quarter adjusted EBITDA margin was 26%, down 120 basis points. This is a sequential improvement versus fourth quarter of 20 [Phonetic] basis points as we remain focused on margin expansion.
I will discuss the drivers of first quarter adjusted EBITDA on the next slide. On a GAAP basis, our Q1 effective tax rate of 21.5% versus last year's first quarter effective tax of 22.2% decreased primarily due to a fair discrete item. First quarter net income was $121 million, generating EPS of $1.60. Adjusted net income was $143 million with adjusted EPS of $1.88, down $0.21 from the prior year first quarter.
Finally, free cash flow for the quarter was $137 million, up 13% over the prior year period. We achieved a conversion rate of 95% of adjusted net income, mainly driven by lower variable compensation payments and capital expenditures despite lower adjusted net income. On an organic basis, we drove more than $78 million of inventory reduction over the last 12 months, and we saw inventory turns improve 0.4 turn year-over-year. Slide 5.
Moving on to Slide 5, which details the driver of our first quarter adjusted EBITDA. For the first quarter, adjusted EBITDA decreased by $22 million compared to the first quarter of 2023. Our 6% organic sales reduction unfavorably impacted adjusted EBITDA by $29 million flowing through at our prior year adjusted gross margin rate. Price/cost was accretive to margins and we drove operational productivity that offset employee-related inflation. These results yielded in a negative 50% organic flow through.
The impact of FX and acquisitions net of divestitures contributed $3 million of adjusted EBITDA in the quarter, resulting in a negative 48% flow-through. With that, I'll provide a deeper look at our segment performance. I'm on Slide 6, within our FMT segment. In our water businesses, municipal project activity remains strong. Note that water sales performance in first quarter of the prior year was favorably impacted by both Hurricane-related backlog execution and the catch-up of a one-month lag treatment of the Nexside [Phonetic] acquisition effectively recording four months of Nexside sales in the first quarter of 2023.
Our energy business has remained stable with favorable infrastructure tailwinds, offset by a mild winter. Our agricultural businesses continue to be cyclically down, in line with expectations. Finally, Q1 adjusted EBITDA margins expanded 60 basis points, driven by price/cost and operational productivity despite slightly lower volumes.
Moving on to Page 7. Despite challenging year-over-year comparables, the Health & Science Technologies segment performed to expectations, and nearly all of our HST business saw sequential orders improvement as compared to the fourth quarter. Our teams continue focusing on our most strategic customers' next-gen solutions in life sciences and analytical instrumentation while we watch for signs of recovery.
Our space broadband and laser communication initiatives continue on track despite current quarter customer delays. Our material processing technology business saw strength in food and sports nutrition that offset derivative customer capital investments within biopharma and pharma.
For semiconductor, we saw orders improved above year-over-year and compared to the fourth quarter. And we expect these trends to continue in line with an improved outlook for memory chips. In line with our FMT industrial businesses, the HST industrials are steady.
Lastly, adjusted EBITDA margins improved 40 basis points over the fourth quarter of last year. A year-over-year decline of 250 basis points was driven by volume leverage, partially offset by price/cost and operational productivity.
Now turning to Slide 8. Our Fire & Safety/Diversified Products segment performance was driven by dispensing project wins in emerging markets, which helped offset the impact of key U.S. customers' multiyear refreshment cycle. We continue to see stability in Fire & Safety. In the quarter, our focus on strategic share gain initiatives helped partially offset unfavorable budget reallocations in the industry. BAND-IT automotive demand is strong with growth expected in the year.
Additionally, industrial performance was similar to FMT and HST with sequential improvement versus Q4. Finally, adjusted EBITDA margins expanded 40 basis points, driven by price/cost. With that, I'd like to provide an update on our outlook for the second quarter. I'm on Slide 9. In Q2, we're projecting GAAP EPS to range from $1.75 to $1.80 and adjusted EPS to range from $2 to $2.05, with organic revenue decline of approximately 2% to 3% and adjusted EBITDA margin of approximately 27.5%. Turning to the full year 2024. We are maintaining our previously issued full year outlook of organic revenue growth of 0% to 2% and adjusted EBITDA margin of approximately 28% and adjusted EPS of $8.15 to $8.45 with majority of markets performing in line with our initial guidance and our focused efforts on driving growth bets.
With that, I'll turn it over to Eric for his closing remarks.